Histopathology 1992. 20, 99-106
Mammary hamartoma-a
review of 3 5 cases
C.J.FISHER, A.M.HANBY, L.ROBINSON* & R.R.MILLIS lmperial Cancer Research Fund Clinical Oncology Unit and *Department of Radiology, Guy Is Hospital. London, UK Date of submission 14 June 199 I Accepted for publication 2 September 1991
F I S H E R C.J., H A N B Y A . M . , R O B I N S O N L . & M I L L I S R . R .
(1992) Histopathology 20, 99-106
Mammary hamartoma-a
review of 35 cases
Mammary hamartomas are macroscopically well-delineated tumours composed of a variable mixture of epithelial elements, fat and fibrous tissue. Such lesions are a n under-recognized entity and, as they can be visualized by mammography, may be seen more frequently with the advent of the UK National Breast Screening Programme. The clinical and pathological features of 3 5 cases of mammary hamartoma seen at the Imperial Cancer Research Fund Clinical Oncology Unit at Guy’s Hospital between 1979 and 1990 have been reviewed. Hormone receptor analysis on nine cases gave high progesterone with low oestrogen levels, probably reflecting their pretnenopausal status. Immunohistochemistry showed that the positive receptor staining was confined to the epithelial elements. In 2 5 cases pseudo-angiomatous hyperplasia was evident in the stroma of the lesion. The importance of distinguishing the interanastomosing stromal spaces seen in the latter condition from low-grade angiosarcoma is emphasized; the relationship between pseudo-angiomatous hyperplasia and mammary hamartoma is discussed; and the possibility that the former represents a permanently dilated form of the lymphatic labyrinth suggested. Keywords: mammary hamartoma, pseudo-angiomatous hyperplasia, lymphatic labyrinth
Introduction The term mammary hamartoma was introduced by Arrigoni et al. in 1971’ to describe well-circumscribed lesions in the breast characterized by varying amounts of benign epithelial elements, fibrous tissue and fat. Such lesions have been known by various names, including fibroadenolipoma, a composite term reflecting the histological features. Mammary hamartoma is not a wellrecognized entity. This is probably because it can be diagnosed with certainty only by using a combination of clinical, radiological, gross and microscopic pathological features. Indeed, in the Imperial Cancer Research Fund Guy’s Hospital Breast Unit only 3 5 cases of mammary hamartoma have been recorded in the past 11 years. These 3 5 cases show a spectrum of histological changes, including pseudo-angiomatous hyperplasia. Pseudo-angiomatous hyperplasia is the term applied to a striking stromal change, originally described by Vuitch et al.’, consisting of a complex pattern of interanastomosing spaces, lined by cells resembling endothelium, and simulating a vascular lesion. The aetiology is Address for correspondence: Dr C.J.Fisher. ICRF Clinical Oncology Unit. Guy’s Hospital, London SE1 9RT, UK.
unknown but Vuitch et al.* suggested that it might result from a stromal response to progesterone in oestrogenprimed tissue. In order to further characterize the entity of mammary hamartoma and its relationship to pseudo-angiomatous hyperplasia, a histological review of these 3 5 cases has been undertaken. The stromal features have been evaluated by immunohistochemistry, using a panel of antibodies; where frozen tissue was available, oestrogen and progesterone receptor analyses were also carried out.
Materials and methods Thirty-five cases, diagnosed as mammary hamartoma between mid-19 79 and mid-1 990, were retrieved from the files of the ICRF Breast Unit. During this 11-year period approximately 7500 breast biopsies were seen in the unit: 4500 benign and 3000 malignant. The clinical notes of the patients were studied and, where available, the mammograms were reassessed. The histological slides were all reviewed, and immunohistochemistry was carried out using a panel of antibodies (Table 1)on formalin-fixed, paraffin-embed99
100 C.j.Fisher et al.
Table 1. Antibodies and lectin used
Source von Willebrand’s factor (factor Dako VIII-related antigen) QBEND/ 10 Dako Virnentin Euro Tech Collagen IV Dako Anti-a-smooth Euro Diagnostics: muscle actin ICN Desmin Dako Uiex europaeus Sigma agglutinin type 1
Dilution l/lO0
1/20 1/10 1/100 1/400 1/10 1/150
ded tissue. The antibodies were chosen with a view to evaluating the stromal components within the lesions and studying the areas of pseudo-angiomatous hyperplasia. A peroxidase-conjugated streptavidin-biotin complex technique was used at the dilutions shown. Frozen tissue was available from nine biopsies for hormone receptor analysis. Both cytosolic and immunohistochemical methods were employed. Cytosols were prepared from tissue frozen soon after surgical removal from the patient, and the levels of oestrogen and progesterone receptors present were measured quantitatively using Abbott Enzyme Immunoassay kits. Cryostat sections of the frozen tissue were immunostained using the Abbott Immunocytochemical Monoclonal Assay kit for the detection of oestrogen receptor protein and the monoclonal antibody mPR1, supplied by Transbio, for the detection of progesterone receptor protein. This latter antibody was applied using a peroxidase-conjugated streptavidin-biotin labelling method at a dilution of 1/300.
Results CLINICAL AND M A M M O G R A P H I C FEATURES
The 35 lesions all occurred in women who were aged between 1 3 and 53 years (median 30 years). The majority of patients (30)presented with a single palpable lump, including one woman who was pregnant. One other woman had multiple lumps within the same breast, Two of these were biopsied, one was a mammary hamartoma but the other proved to be an invasive ductal carcinoma. The remaining four women, including two young pubertal girls, presented with unilateral mammary hypertrophy. All the lesions were removed at open biopsy and none, to our knowledge, has recurred.
Figure 1. Mammogram showing the classical appearances of a mammary hamartoma. Note the rounded outline. pseudo-capsule and variable opacity of the lesion.
Ten of the women had pre-operative mammograms. Seven of these showed well-defined, rounded, uniform opacities which in two cases were surrounded by clear halos. One mammogram showed a dense mass which replaced the entire breast, and another had bilateral patchy dense breasts without a specific lesion. The tenth mammogram, from the oldest woman in our series, showed the appearances, considered to be classical3,of a mammary hamartoma (Figure 1).It showed a rounded lesion of variable opacity which appeared to be surrounded by a capsule. PATHOLOGICAL FEATURES
Gross appearance On macroscopic examination the lesions were described as being well-defined, with a smooth, glistening surface, often having a disc-like or lentiform shape. Sometimes
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101
Figure 2. Cut surface of a mammary hamartoma showing the circumscription. The lesion was soft, mottled yellow and grey with a moderate amount of adipose tissue present.
they resembled a soft, yellow fibroadenoma, but lacked the clefts often seen on the cut surface of these tumours (Figure 2). The amount of adipose tissue varied and lesions that contained little or no fat, were firm and rubbery. The lesional maximum diameter ranged from 1 . 3 to 24 cm.
Figure 3. Low-power view showing the entire cross-section of a mammary hamartoma that ‘shelled out’ at operation. In this lesion cyst formation was a prominent feature. H & E.
Microscopic features Histological examination revealed a combination of epithelial and stromal elements (Figure 3 ) . Plentiful lobules were seen which, in the two pubertal cases, were poorly formed. In some cases the lobules were discrete and the histological picture was that of normal breast. In others the glandular elements were randomly dispersed with varying degrees of lobular distortion. Small cysts were a frequent finding; apocrine change was occasionally seen, but epithelial hyperplasia only rarely. In no case was there any evidence of atypia.
The pattern of the stroma was variable but differed from that seen in both normal breast and fibroadenomas (Figure 4). In most cases it was densely fibrous and hyaline and extended into the lobules, obliterating the specialized intralobular stroma. This often resulted in a distinct concentric band of dense collagen surrounding the individual acini (Figure 5). The nodular pattern often seen in fibroadenomas was lacking and, furthermore, neither the slit-like compression of epithelial elements nor the circumferential arrangement of fibrous stroma around individual epithelial components, typical of
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Figure 4. Low-power view of a mammary hamartoma showing the circumscription and surrounding compressed breast tissue. There is increased fibrosis of both inter- and intralobular areas. In this case muscle is also present within the interlobular stroma. H & E.
Figure 5. Mammary hamartoma showing the dense interlobular fibrous tissue extending into the lobules and the bands of dense collagen arranged around individual acini. H Rr E.
fibroadenomas, were seen. The amount of stromal fat was very variable and, indeed, was entirely absent from nine lesions. No correlation was found between the amount of stromal adipose tissue present and the patient's age. In two cases abundant smooth muscle was seen within the stroma. In 2 5 (71%) of the lesions, including those from the youngest and the oldest patients in our series, the stroma contained a network of interanastomosing, slit-like spaces which appeared to be lined by flattened cells. The overall appearance fitted the description of pseudoangiomatous hyperplasia given by Vuitch et d 2in 1986 (Figure 6). This pattern was present to a variable degree in these 2 5 cases and was particularly prominent when the stroma was densely fibrotic. It was often centred around lobules where the spaces were seen both within and concentrically surrounding the lobule.
lmmunohistochemistry The flattened cells lining the pseudo-angiomatous areas showed no reaction with antibody to von Willebrand's factor or with the lectin Ulex europaeus agglutinin type 1 (UEA-l), but did show cytoplasmic staining with antibody to vimentin and with QBEND/104. With vimentin the staining was often very strong and emphasized the pseudo-angiomatous areas (Figure 7). Both these positively staining antibodies, however, also reacted with numerous other stromal cells, especially within and immediately surrounding the lobules. In five cases the flattened cells lining the spaces also stained with antibodies to actin. Antibodies to collagen IV identified the basement membrane around the epithelial elements but showed no staining around the spaces within the pseudoangiomatous areas.
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Figure 6. Mammary hamartoma showing the interanastomosing cleft-like spaces of pseudo-angiomatous hyperplasia within the strorna. The spaces are lined by flattened cells. H (L E.
Figure 7. Staining for vimentin of the same lesion as Figure 6, emphasizing the areas of pseudo-angiomatous hyperplasia.
In the two cases in which smooth muscle was identified in the haematoxylin and eosin stained sections, immunohistochemistry showed strong staining of these areas with antibodies to actin and desmin. In another 19 cases variable numbers of scattered stromal cells also showed positive staining with these two antibodies (Figure 8). All nine cases in which cytosolic steroid hormone receptor analysis was carried out were oestrogen receptor negative (< 2 0 fmol/mg protein) (Table 2 ) , but six were progesterone receptor positive (> 2 0 fmol/mg protein). Immunohistochemical staining of frozen sections with antibodies to both progesterone and oestrogen receptors showed positive staining in varying numbers of epithelial cells in all nine cases, with the greatest intensity and number of positive cells being seen with the antibody to progesterone receptor. No staining was seen in the stromal elements. Six of these nine cases included areas of pseudo-angiomatous hyperplasia, but no stain-
ing was seen in these areas. None of the nine cases contained smooth muscle.
Discussion Well-circumscribed breast tumours, often consisting of normal mammary tissue were originally described in 1928 by Prym5 who called them mastomas. The terms adenolipoma and fibroadenolipoma have also been applied to comparable, and probably identical, lesions. Similar lesions that contain a significant amount of smooth muscle within the stroma have been called muscular hamartomas'. The spectrum of appearances seen in these lesions no doubt accounts for the variable terminology which has been applied to them. The name mammary hamartoma was introduced in 197 1 by Arrigoni et dl,who emphasized the encapsulation of the lesions and further characterized the diagnosis as one of exclusion, with histological configurations not represen-
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41.
Tabte 2. Steroid hormone receptor analyses
Cytosolic receptor level (fmol/mg protein) Patient age
PAH
Oestrogen
Progesterone __
27 29 17 35 33 16 20
14 13
Present Present Present Absent Absent Present Absent Present Present
15 0 3
5 9 0 0 6 0
99 1 110 134 49 6 2 94 28
PAH = pseudo-angiomatous hyperplasia.
Figure 8, Staining for a-actin showing positive stromal cells arranged in a longitudinal fashion.
tative of fibroadenoma, lactating adenoma or other wellcharacterized benign mammary tumour. The appropriateness of the term mammary hamartoma has been questioned, one point being that it is not congenital but, as the fully developed mammary gland is not present at birth, strict criteria cannot be applied in this situation. Mammary hamartoma remains the most fitting name so far applied to these lesions. Mammary hamartomas have been reported at all ages. The patients in our series range from 1 3 to 5 3 years, but similar lesions have been described in women as old as 88 years3. So far no case has been reported in a male. Hogeman & Ostberg’ considered the condition to be secondary to lactation, but in most series, including our own, no relationship has been found with pregnancy or lactation. The lesions can grow to a large size and produce marked asymmetry of the breasts. The two youngest patients in our series, aged 1 3 and 14 years respectively, presented with unilateral mammary enlargement initially diagnosed as virginal hypertrophy. This resulted in considerable delay in treatment for one of the patients; her tumour weighed 2953 g when surgery was finally resorted to, when the lesion was found to shell out easily. Mammography of mammary hamartomas usually reveals a sharply circumscribed density which may have a mottled appearance due to the varying proportion of stromal fatty and fibrous tissue. The adjacent breast tissue is displaced, often with an intervening, thin, radiolucent zone. Relatively large lesions have been detected on mammography in the absence of clinical findings. Although Arrigoni et a].’ emphasized the encapsulation of mammary hamartomas, the lesions in our series did not have a true fibrous capsule, but were surrounded by compressed adjacent mammary tissue. The macroscopic appearance is important when making the diagnosis of mammary hamartoma. On histological examination, there is such a spectrum of change, ranging from normal mammary tissue to the full gamut of change seen in benign breast disease, that if the smooth outline and well-demarcated nature of the lesion is not noted on gross examination the diagnosis can easily be missed. Earlier descriptions of mammary hamartomas noted plentiful fat in the stroma, but in our series the amount of fat was very variable and, in nine cases, was entirely absent. In such cases the diagnosis of fibroadenoma must be excluded and only those lesions that do not show the characteristic features of a fibroadenoma should be called hamartomas. The origin of the smooth muscle in muscular hamartomas is not known but it is worthy of note that 58% of the mammary hamartomas in our series contained
Mammary hamartoma
scattered stromal cells that reacted positively with immunohistochemical markers for muscle. These elongated spindle shaped cells could be myofibroblasts or even isolated smooth muscle cells (Figure 8). Line11 et aL8 commented on the marked vascularity of the stroma of mammary hamartomas, and this feature was also reported in many of the cases diagnosed early in our series. Following the description of pseudo-angiomatous hyperplasia by Vuitch et aL2, however, the stromal changes in our cases of mammary hamartoma were recognized to be similar. The theory that the anastomosing channels, indeed, represented pseudo-angiomatous rather than true angiomatous hyperplasia was supported by the immunohistochemistry that we subsequently carried out. It is, obviously, vitaily important that pseudo-angiomatous hyperplasia is differentiated from true vascular hyperplasia as, otherwise, it can be confused with low-grade angiosarcoma; indeed this diagnosis was initially considered in one of the cases of mammary hamartoma in our series. In a recent report, Anderson et aL9 concluded that pseudo-angiomatous hyperplasia should not be included in the diagnostic range of mammary hamartomas. They argued, first, that hamartomas are not known to recur whereas, they concluded, two of Vuitch's original nine cases did. Vuitch et aL2 however, felt that they were not true recurrences, as the original excision may have been incomplete. Anderson et also found that, while the epithelium both in cases of isolated pseudo-angiomatous hyperplasia and mammary hamartomas stained positively with antibodies to progesterone receptor, there were differences in the staining of the stromal cells. In pseudo-angiomatous hyperplasia the stromal cells showed patchy, intense labelling for progesterone receptor protein, whereas the stroma in mammary hamartomas only labelled inconsistently. None of the areas of pseudo-angiomatous hyperplasia in our series reacted with antibodies to either oestrogen or progesterone receptor protein. In our view pseudo-angiomatous hyperplasia may form part of the spectrum of changes seen within mammary hamartomas. It is a not uncommon histological finding in breast biopsy material. Ibrahim et al.") identified the change in 23% of 200 consecutive breast specimens and concluded that it occurred as a spectrum from microscopic foci to lesions where the change resulted in a breast mass. The pseudo-angiomatous hyperplasia in our series of mammary hamartomas ranged in size from microscopic areas to a generalized stromal change. It seems logical, therefore, that areas of pseudo-angiomatous hyperplasia that form a macroscopically identifiable mass should be included within the diagnostic category of mammary hamartoma. Vuitch et aL2 considered that pseudo-angiomatous
105
hyperplasia might originate as a response to progesterone in oestrogen-primed tissue. Their nine cases were all from premenopausal women. This suggestion stimulated us to carry out receptor analysis on'our cases. Of our nine mammary hamartomas that were assayed, all were oestrogen receptor negative, but six, including four which demonstrated pseudo-angiomatous hyperplasia, were progesterone receptor positive. In a study of a range of benign mammary lesions, Giani et al." noted similar findings in 31 fibroadenomas and one mammary hamartoma. They further found that proliferation of epithelial components correlated with progesterone receptor positivity. Immunohistochemical examination of frozen sections in our cases of mammary hamartoma, with antibodies to oestrogen and progesterone receptor, confirmed that all the receptor activity was within the epithelial element and that staining with progesterone receptor antibody was always stronger. Jacquemier et however, have found that in normal breast tissue and benign lumps from premenopausal women a greater number of epithelial cells express progesterone receptors than oestrogen receptors, and all our lesions on which receptor analyses were done were from women 3 5 years and under. Histologically, pseudo-angiomatous hyperplasia is characterized by dense hyaline fibrous stroma containing irregular, empty, anastomosing, slit-like spaces lined by flattened cells. Its aetiology is not known, but it does not appear to be artefactual, as it is seen in frozen sections as well as fixed material. Recently Hartveit' has described the missing lymphatic system of the breast, that she has termed the lymphatic labyrinth. This is made up of fine lymphatic vessels, sinusoids and potential spaces lined, on one side only, by flattened cells. It may be that pseudo-angiomatous hyperplasia is a permanently dilated and sclerotic form of this labyrinth. Immunohistochemistry in our cases showed a lack of staining in these areas with the vascular markers von Willebrand's factor and UEA-I, but did show positive staining with QBEND/10 and vimentin, both of which stain lymphatic endothelial cells. This result has to be interpreted with caution because of the presence of positive staining in numerous other stromal cells with both of the latter antibodies. Unfortunately, samples of tissue taken for ultrastructural study from two more recently diagnosed cases of mammary hamartoma did not include areas of pseudo-angiomatous hyperplasia. However, electronmicroscopy has been performed on both the lymphatic labyrinth13 and pseudo-angiomatous hyperplasia2."'. Both conditions showed spaces lined by slender cells with tapering cytoplasmic processes that, again, could be either fibroblasts or lymphatic endothelial cells. The purpose of this report is to draw attention to the
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underdiagnosed entity mammary hamartoma which, as it can present as a mammographic abnormality, may be seen more frequently in patients entering the National Breast Screening Programme. It is, therefore, important that the entity is recognized so that accurate and satisfactory correlation can be made with the mammographic appearances. The frequent presence of pseudo-angiomatous hyperplasia within mammary hamartomas is another reason for their recognition, as it is also important that this latter condition is correctly diagnosed and distinguished from low-grade angiosarcoma.
Acknowledgements The authors are grateful to Dr M.A.Parsons, University of Sheffield Medical School, for permission to include one of the cases.
References 1. Arrigoni MG, Dockerty MB, Judd ES. The identification and treatment of mammary hamartoma. Surg. Gynecol. Obstet. 1971: 133; 577-582. 2. Vuitch MF. Rosen PP, Erlandson RA. Pseudoangiomatous hyperplasia of mammary stroma. Hum. Pathol. 1986; 17; 185-191. 3. Hessler C, Schnyder P, Ozzello L. Hamartoma of the breast: diagnostic observation of 16 cases. Radiology 1978: 126; 95-98.
4. Ramani P. Bradley N]. Fletcher CDM. QBEND/lo, a new monoclonal antibody to endothelium: assessment of its diagnostic utility in paraffin sections. Histopathology 1990: 17; 237-242. 5. Prym P. Pseudoadenome. adenome und mastome der weiblichen brustdruse. Beitr. Pathol. Anat. 1928: 81: 1-44. 6. Davies JD, Riddell RH. Muscular hamartomas of the breast. 1. Pathol. 1973; 111; 209-211. 7. Hogeman K-E, Ostberg G. Three cases of postlactational breast tumour of a peculiar type. Acta Pathol. Microbiol. Scand. 1968: 73; 169-176. 8. Linell F. Ostberg G. Soderstrom J, Andersson I. Hildell J, Ljungqvist U. Breast hamartomas: an important entity in mammary pathology. Virchows Arch. [Pathol. Atiat. Histol.] 1979; 383; 253-264. 9. Anderson C. Ricci A, Pedersen CA. Cartun RW. Immunocytochemica1 analysis of oestrogen and progesterone receptors in benign stromal lesions of the breast. Am. J. Surg. Pathol. 1991: 15; 145149. 10. Ibrahim RE, Sciotto CG. Weidner N. Pseudoangiomatous hyperplasia of mammary stroma. Some observations regarding its clinicopathologic spectrum. Cancer 1989: 63; 1154-1 160. 11. Giani C, D’Amore E. Delarue JC et al. Oestrogen and progesterone receptors in benign breast tumours and lesions: relationship with histological and cytological features. Int. 1. Cancer 1986: 37; 7-10. 12. Jacquemier JD, Hassoun J. Torrente M. Martin P-M. Distribution of oestrogen and progesterone receptors in healthy tissue adjacent to breast lesions at various stages-immunohistochemical study of 107 cases. Breast Cancer Res. Treat. 1990; 15; 109-117. 13. Hartveit F. Attenuated cells in breast stroma: the missing lymphatic system of the breast. Histopathology 1990: 16; 533543.
Mammary hamartoma-a
review of 3 5 cases
C.J.FISHER, A.M.HANBY, L.ROBINSON* & R.R.MILLIS lmperial Cancer Research Fund Clinical Oncology Unit and *Department of Radiology, Guy Is Hospital. London, UK Date of submission 14 June 199 I Accepted for publication 2 September 1991
F I S H E R C.J., H A N B Y A . M . , R O B I N S O N L . & M I L L I S R . R .
(1992) Histopathology 20, 99-106
Mammary hamartoma-a
review of 35 cases
Mammary hamartomas are macroscopically well-delineated tumours composed of a variable mixture of epithelial elements, fat and fibrous tissue. Such lesions are a n under-recognized entity and, as they can be visualized by mammography, may be seen more frequently with the advent of the UK National Breast Screening Programme. The clinical and pathological features of 3 5 cases of mammary hamartoma seen at the Imperial Cancer Research Fund Clinical Oncology Unit at Guy’s Hospital between 1979 and 1990 have been reviewed. Hormone receptor analysis on nine cases gave high progesterone with low oestrogen levels, probably reflecting their pretnenopausal status. Immunohistochemistry showed that the positive receptor staining was confined to the epithelial elements. In 2 5 cases pseudo-angiomatous hyperplasia was evident in the stroma of the lesion. The importance of distinguishing the interanastomosing stromal spaces seen in the latter condition from low-grade angiosarcoma is emphasized; the relationship between pseudo-angiomatous hyperplasia and mammary hamartoma is discussed; and the possibility that the former represents a permanently dilated form of the lymphatic labyrinth suggested. Keywords: mammary hamartoma, pseudo-angiomatous hyperplasia, lymphatic labyrinth
Introduction The term mammary hamartoma was introduced by Arrigoni et al. in 1971’ to describe well-circumscribed lesions in the breast characterized by varying amounts of benign epithelial elements, fibrous tissue and fat. Such lesions have been known by various names, including fibroadenolipoma, a composite term reflecting the histological features. Mammary hamartoma is not a wellrecognized entity. This is probably because it can be diagnosed with certainty only by using a combination of clinical, radiological, gross and microscopic pathological features. Indeed, in the Imperial Cancer Research Fund Guy’s Hospital Breast Unit only 3 5 cases of mammary hamartoma have been recorded in the past 11 years. These 3 5 cases show a spectrum of histological changes, including pseudo-angiomatous hyperplasia. Pseudo-angiomatous hyperplasia is the term applied to a striking stromal change, originally described by Vuitch et al.’, consisting of a complex pattern of interanastomosing spaces, lined by cells resembling endothelium, and simulating a vascular lesion. The aetiology is Address for correspondence: Dr C.J.Fisher. ICRF Clinical Oncology Unit. Guy’s Hospital, London SE1 9RT, UK.
unknown but Vuitch et al.* suggested that it might result from a stromal response to progesterone in oestrogenprimed tissue. In order to further characterize the entity of mammary hamartoma and its relationship to pseudo-angiomatous hyperplasia, a histological review of these 3 5 cases has been undertaken. The stromal features have been evaluated by immunohistochemistry, using a panel of antibodies; where frozen tissue was available, oestrogen and progesterone receptor analyses were also carried out.
Materials and methods Thirty-five cases, diagnosed as mammary hamartoma between mid-19 79 and mid-1 990, were retrieved from the files of the ICRF Breast Unit. During this 11-year period approximately 7500 breast biopsies were seen in the unit: 4500 benign and 3000 malignant. The clinical notes of the patients were studied and, where available, the mammograms were reassessed. The histological slides were all reviewed, and immunohistochemistry was carried out using a panel of antibodies (Table 1)on formalin-fixed, paraffin-embed99
100 C.j.Fisher et al.
Table 1. Antibodies and lectin used
Source von Willebrand’s factor (factor Dako VIII-related antigen) QBEND/ 10 Dako Virnentin Euro Tech Collagen IV Dako Anti-a-smooth Euro Diagnostics: muscle actin ICN Desmin Dako Uiex europaeus Sigma agglutinin type 1
Dilution l/lO0
1/20 1/10 1/100 1/400 1/10 1/150
ded tissue. The antibodies were chosen with a view to evaluating the stromal components within the lesions and studying the areas of pseudo-angiomatous hyperplasia. A peroxidase-conjugated streptavidin-biotin complex technique was used at the dilutions shown. Frozen tissue was available from nine biopsies for hormone receptor analysis. Both cytosolic and immunohistochemical methods were employed. Cytosols were prepared from tissue frozen soon after surgical removal from the patient, and the levels of oestrogen and progesterone receptors present were measured quantitatively using Abbott Enzyme Immunoassay kits. Cryostat sections of the frozen tissue were immunostained using the Abbott Immunocytochemical Monoclonal Assay kit for the detection of oestrogen receptor protein and the monoclonal antibody mPR1, supplied by Transbio, for the detection of progesterone receptor protein. This latter antibody was applied using a peroxidase-conjugated streptavidin-biotin labelling method at a dilution of 1/300.
Results CLINICAL AND M A M M O G R A P H I C FEATURES
The 35 lesions all occurred in women who were aged between 1 3 and 53 years (median 30 years). The majority of patients (30)presented with a single palpable lump, including one woman who was pregnant. One other woman had multiple lumps within the same breast, Two of these were biopsied, one was a mammary hamartoma but the other proved to be an invasive ductal carcinoma. The remaining four women, including two young pubertal girls, presented with unilateral mammary hypertrophy. All the lesions were removed at open biopsy and none, to our knowledge, has recurred.
Figure 1. Mammogram showing the classical appearances of a mammary hamartoma. Note the rounded outline. pseudo-capsule and variable opacity of the lesion.
Ten of the women had pre-operative mammograms. Seven of these showed well-defined, rounded, uniform opacities which in two cases were surrounded by clear halos. One mammogram showed a dense mass which replaced the entire breast, and another had bilateral patchy dense breasts without a specific lesion. The tenth mammogram, from the oldest woman in our series, showed the appearances, considered to be classical3,of a mammary hamartoma (Figure 1).It showed a rounded lesion of variable opacity which appeared to be surrounded by a capsule. PATHOLOGICAL FEATURES
Gross appearance On macroscopic examination the lesions were described as being well-defined, with a smooth, glistening surface, often having a disc-like or lentiform shape. Sometimes
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101
Figure 2. Cut surface of a mammary hamartoma showing the circumscription. The lesion was soft, mottled yellow and grey with a moderate amount of adipose tissue present.
they resembled a soft, yellow fibroadenoma, but lacked the clefts often seen on the cut surface of these tumours (Figure 2). The amount of adipose tissue varied and lesions that contained little or no fat, were firm and rubbery. The lesional maximum diameter ranged from 1 . 3 to 24 cm.
Figure 3. Low-power view showing the entire cross-section of a mammary hamartoma that ‘shelled out’ at operation. In this lesion cyst formation was a prominent feature. H & E.
Microscopic features Histological examination revealed a combination of epithelial and stromal elements (Figure 3 ) . Plentiful lobules were seen which, in the two pubertal cases, were poorly formed. In some cases the lobules were discrete and the histological picture was that of normal breast. In others the glandular elements were randomly dispersed with varying degrees of lobular distortion. Small cysts were a frequent finding; apocrine change was occasionally seen, but epithelial hyperplasia only rarely. In no case was there any evidence of atypia.
The pattern of the stroma was variable but differed from that seen in both normal breast and fibroadenomas (Figure 4). In most cases it was densely fibrous and hyaline and extended into the lobules, obliterating the specialized intralobular stroma. This often resulted in a distinct concentric band of dense collagen surrounding the individual acini (Figure 5). The nodular pattern often seen in fibroadenomas was lacking and, furthermore, neither the slit-like compression of epithelial elements nor the circumferential arrangement of fibrous stroma around individual epithelial components, typical of
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Figure 4. Low-power view of a mammary hamartoma showing the circumscription and surrounding compressed breast tissue. There is increased fibrosis of both inter- and intralobular areas. In this case muscle is also present within the interlobular stroma. H & E.
Figure 5. Mammary hamartoma showing the dense interlobular fibrous tissue extending into the lobules and the bands of dense collagen arranged around individual acini. H Rr E.
fibroadenomas, were seen. The amount of stromal fat was very variable and, indeed, was entirely absent from nine lesions. No correlation was found between the amount of stromal adipose tissue present and the patient's age. In two cases abundant smooth muscle was seen within the stroma. In 2 5 (71%) of the lesions, including those from the youngest and the oldest patients in our series, the stroma contained a network of interanastomosing, slit-like spaces which appeared to be lined by flattened cells. The overall appearance fitted the description of pseudoangiomatous hyperplasia given by Vuitch et d 2in 1986 (Figure 6). This pattern was present to a variable degree in these 2 5 cases and was particularly prominent when the stroma was densely fibrotic. It was often centred around lobules where the spaces were seen both within and concentrically surrounding the lobule.
lmmunohistochemistry The flattened cells lining the pseudo-angiomatous areas showed no reaction with antibody to von Willebrand's factor or with the lectin Ulex europaeus agglutinin type 1 (UEA-l), but did show cytoplasmic staining with antibody to vimentin and with QBEND/104. With vimentin the staining was often very strong and emphasized the pseudo-angiomatous areas (Figure 7). Both these positively staining antibodies, however, also reacted with numerous other stromal cells, especially within and immediately surrounding the lobules. In five cases the flattened cells lining the spaces also stained with antibodies to actin. Antibodies to collagen IV identified the basement membrane around the epithelial elements but showed no staining around the spaces within the pseudoangiomatous areas.
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Figure 6. Mammary hamartoma showing the interanastomosing cleft-like spaces of pseudo-angiomatous hyperplasia within the strorna. The spaces are lined by flattened cells. H (L E.
Figure 7. Staining for vimentin of the same lesion as Figure 6, emphasizing the areas of pseudo-angiomatous hyperplasia.
In the two cases in which smooth muscle was identified in the haematoxylin and eosin stained sections, immunohistochemistry showed strong staining of these areas with antibodies to actin and desmin. In another 19 cases variable numbers of scattered stromal cells also showed positive staining with these two antibodies (Figure 8). All nine cases in which cytosolic steroid hormone receptor analysis was carried out were oestrogen receptor negative (< 2 0 fmol/mg protein) (Table 2 ) , but six were progesterone receptor positive (> 2 0 fmol/mg protein). Immunohistochemical staining of frozen sections with antibodies to both progesterone and oestrogen receptors showed positive staining in varying numbers of epithelial cells in all nine cases, with the greatest intensity and number of positive cells being seen with the antibody to progesterone receptor. No staining was seen in the stromal elements. Six of these nine cases included areas of pseudo-angiomatous hyperplasia, but no stain-
ing was seen in these areas. None of the nine cases contained smooth muscle.
Discussion Well-circumscribed breast tumours, often consisting of normal mammary tissue were originally described in 1928 by Prym5 who called them mastomas. The terms adenolipoma and fibroadenolipoma have also been applied to comparable, and probably identical, lesions. Similar lesions that contain a significant amount of smooth muscle within the stroma have been called muscular hamartomas'. The spectrum of appearances seen in these lesions no doubt accounts for the variable terminology which has been applied to them. The name mammary hamartoma was introduced in 197 1 by Arrigoni et dl,who emphasized the encapsulation of the lesions and further characterized the diagnosis as one of exclusion, with histological configurations not represen-
104
C.J.Fisher et
41.
Tabte 2. Steroid hormone receptor analyses
Cytosolic receptor level (fmol/mg protein) Patient age
PAH
Oestrogen
Progesterone __
27 29 17 35 33 16 20
14 13
Present Present Present Absent Absent Present Absent Present Present
15 0 3
5 9 0 0 6 0
99 1 110 134 49 6 2 94 28
PAH = pseudo-angiomatous hyperplasia.
Figure 8, Staining for a-actin showing positive stromal cells arranged in a longitudinal fashion.
tative of fibroadenoma, lactating adenoma or other wellcharacterized benign mammary tumour. The appropriateness of the term mammary hamartoma has been questioned, one point being that it is not congenital but, as the fully developed mammary gland is not present at birth, strict criteria cannot be applied in this situation. Mammary hamartoma remains the most fitting name so far applied to these lesions. Mammary hamartomas have been reported at all ages. The patients in our series range from 1 3 to 5 3 years, but similar lesions have been described in women as old as 88 years3. So far no case has been reported in a male. Hogeman & Ostberg’ considered the condition to be secondary to lactation, but in most series, including our own, no relationship has been found with pregnancy or lactation. The lesions can grow to a large size and produce marked asymmetry of the breasts. The two youngest patients in our series, aged 1 3 and 14 years respectively, presented with unilateral mammary enlargement initially diagnosed as virginal hypertrophy. This resulted in considerable delay in treatment for one of the patients; her tumour weighed 2953 g when surgery was finally resorted to, when the lesion was found to shell out easily. Mammography of mammary hamartomas usually reveals a sharply circumscribed density which may have a mottled appearance due to the varying proportion of stromal fatty and fibrous tissue. The adjacent breast tissue is displaced, often with an intervening, thin, radiolucent zone. Relatively large lesions have been detected on mammography in the absence of clinical findings. Although Arrigoni et a].’ emphasized the encapsulation of mammary hamartomas, the lesions in our series did not have a true fibrous capsule, but were surrounded by compressed adjacent mammary tissue. The macroscopic appearance is important when making the diagnosis of mammary hamartoma. On histological examination, there is such a spectrum of change, ranging from normal mammary tissue to the full gamut of change seen in benign breast disease, that if the smooth outline and well-demarcated nature of the lesion is not noted on gross examination the diagnosis can easily be missed. Earlier descriptions of mammary hamartomas noted plentiful fat in the stroma, but in our series the amount of fat was very variable and, in nine cases, was entirely absent. In such cases the diagnosis of fibroadenoma must be excluded and only those lesions that do not show the characteristic features of a fibroadenoma should be called hamartomas. The origin of the smooth muscle in muscular hamartomas is not known but it is worthy of note that 58% of the mammary hamartomas in our series contained
Mammary hamartoma
scattered stromal cells that reacted positively with immunohistochemical markers for muscle. These elongated spindle shaped cells could be myofibroblasts or even isolated smooth muscle cells (Figure 8). Line11 et aL8 commented on the marked vascularity of the stroma of mammary hamartomas, and this feature was also reported in many of the cases diagnosed early in our series. Following the description of pseudo-angiomatous hyperplasia by Vuitch et aL2, however, the stromal changes in our cases of mammary hamartoma were recognized to be similar. The theory that the anastomosing channels, indeed, represented pseudo-angiomatous rather than true angiomatous hyperplasia was supported by the immunohistochemistry that we subsequently carried out. It is, obviously, vitaily important that pseudo-angiomatous hyperplasia is differentiated from true vascular hyperplasia as, otherwise, it can be confused with low-grade angiosarcoma; indeed this diagnosis was initially considered in one of the cases of mammary hamartoma in our series. In a recent report, Anderson et aL9 concluded that pseudo-angiomatous hyperplasia should not be included in the diagnostic range of mammary hamartomas. They argued, first, that hamartomas are not known to recur whereas, they concluded, two of Vuitch's original nine cases did. Vuitch et aL2 however, felt that they were not true recurrences, as the original excision may have been incomplete. Anderson et also found that, while the epithelium both in cases of isolated pseudo-angiomatous hyperplasia and mammary hamartomas stained positively with antibodies to progesterone receptor, there were differences in the staining of the stromal cells. In pseudo-angiomatous hyperplasia the stromal cells showed patchy, intense labelling for progesterone receptor protein, whereas the stroma in mammary hamartomas only labelled inconsistently. None of the areas of pseudo-angiomatous hyperplasia in our series reacted with antibodies to either oestrogen or progesterone receptor protein. In our view pseudo-angiomatous hyperplasia may form part of the spectrum of changes seen within mammary hamartomas. It is a not uncommon histological finding in breast biopsy material. Ibrahim et al.") identified the change in 23% of 200 consecutive breast specimens and concluded that it occurred as a spectrum from microscopic foci to lesions where the change resulted in a breast mass. The pseudo-angiomatous hyperplasia in our series of mammary hamartomas ranged in size from microscopic areas to a generalized stromal change. It seems logical, therefore, that areas of pseudo-angiomatous hyperplasia that form a macroscopically identifiable mass should be included within the diagnostic category of mammary hamartoma. Vuitch et aL2 considered that pseudo-angiomatous
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hyperplasia might originate as a response to progesterone in oestrogen-primed tissue. Their nine cases were all from premenopausal women. This suggestion stimulated us to carry out receptor analysis on'our cases. Of our nine mammary hamartomas that were assayed, all were oestrogen receptor negative, but six, including four which demonstrated pseudo-angiomatous hyperplasia, were progesterone receptor positive. In a study of a range of benign mammary lesions, Giani et al." noted similar findings in 31 fibroadenomas and one mammary hamartoma. They further found that proliferation of epithelial components correlated with progesterone receptor positivity. Immunohistochemical examination of frozen sections in our cases of mammary hamartoma, with antibodies to oestrogen and progesterone receptor, confirmed that all the receptor activity was within the epithelial element and that staining with progesterone receptor antibody was always stronger. Jacquemier et however, have found that in normal breast tissue and benign lumps from premenopausal women a greater number of epithelial cells express progesterone receptors than oestrogen receptors, and all our lesions on which receptor analyses were done were from women 3 5 years and under. Histologically, pseudo-angiomatous hyperplasia is characterized by dense hyaline fibrous stroma containing irregular, empty, anastomosing, slit-like spaces lined by flattened cells. Its aetiology is not known, but it does not appear to be artefactual, as it is seen in frozen sections as well as fixed material. Recently Hartveit' has described the missing lymphatic system of the breast, that she has termed the lymphatic labyrinth. This is made up of fine lymphatic vessels, sinusoids and potential spaces lined, on one side only, by flattened cells. It may be that pseudo-angiomatous hyperplasia is a permanently dilated and sclerotic form of this labyrinth. Immunohistochemistry in our cases showed a lack of staining in these areas with the vascular markers von Willebrand's factor and UEA-I, but did show positive staining with QBEND/10 and vimentin, both of which stain lymphatic endothelial cells. This result has to be interpreted with caution because of the presence of positive staining in numerous other stromal cells with both of the latter antibodies. Unfortunately, samples of tissue taken for ultrastructural study from two more recently diagnosed cases of mammary hamartoma did not include areas of pseudo-angiomatous hyperplasia. However, electronmicroscopy has been performed on both the lymphatic labyrinth13 and pseudo-angiomatous hyperplasia2."'. Both conditions showed spaces lined by slender cells with tapering cytoplasmic processes that, again, could be either fibroblasts or lymphatic endothelial cells. The purpose of this report is to draw attention to the
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underdiagnosed entity mammary hamartoma which, as it can present as a mammographic abnormality, may be seen more frequently in patients entering the National Breast Screening Programme. It is, therefore, important that the entity is recognized so that accurate and satisfactory correlation can be made with the mammographic appearances. The frequent presence of pseudo-angiomatous hyperplasia within mammary hamartomas is another reason for their recognition, as it is also important that this latter condition is correctly diagnosed and distinguished from low-grade angiosarcoma.
Acknowledgements The authors are grateful to Dr M.A.Parsons, University of Sheffield Medical School, for permission to include one of the cases.
References 1. Arrigoni MG, Dockerty MB, Judd ES. The identification and treatment of mammary hamartoma. Surg. Gynecol. Obstet. 1971: 133; 577-582. 2. Vuitch MF. Rosen PP, Erlandson RA. Pseudoangiomatous hyperplasia of mammary stroma. Hum. Pathol. 1986; 17; 185-191. 3. Hessler C, Schnyder P, Ozzello L. Hamartoma of the breast: diagnostic observation of 16 cases. Radiology 1978: 126; 95-98.
4. Ramani P. Bradley N]. Fletcher CDM. QBEND/lo, a new monoclonal antibody to endothelium: assessment of its diagnostic utility in paraffin sections. Histopathology 1990: 17; 237-242. 5. Prym P. Pseudoadenome. adenome und mastome der weiblichen brustdruse. Beitr. Pathol. Anat. 1928: 81: 1-44. 6. Davies JD, Riddell RH. Muscular hamartomas of the breast. 1. Pathol. 1973; 111; 209-211. 7. Hogeman K-E, Ostberg G. Three cases of postlactational breast tumour of a peculiar type. Acta Pathol. Microbiol. Scand. 1968: 73; 169-176. 8. Linell F. Ostberg G. Soderstrom J, Andersson I. Hildell J, Ljungqvist U. Breast hamartomas: an important entity in mammary pathology. Virchows Arch. [Pathol. Atiat. Histol.] 1979; 383; 253-264. 9. Anderson C. Ricci A, Pedersen CA. Cartun RW. Immunocytochemica1 analysis of oestrogen and progesterone receptors in benign stromal lesions of the breast. Am. J. Surg. Pathol. 1991: 15; 145149. 10. Ibrahim RE, Sciotto CG. Weidner N. Pseudoangiomatous hyperplasia of mammary stroma. Some observations regarding its clinicopathologic spectrum. Cancer 1989: 63; 1154-1 160. 11. Giani C, D’Amore E. Delarue JC et al. Oestrogen and progesterone receptors in benign breast tumours and lesions: relationship with histological and cytological features. Int. 1. Cancer 1986: 37; 7-10. 12. Jacquemier JD, Hassoun J. Torrente M. Martin P-M. Distribution of oestrogen and progesterone receptors in healthy tissue adjacent to breast lesions at various stages-immunohistochemical study of 107 cases. Breast Cancer Res. Treat. 1990; 15; 109-117. 13. Hartveit F. Attenuated cells in breast stroma: the missing lymphatic system of the breast. Histopathology 1990: 16; 533543.
