Pleomorphic Liporna Case Reports and Review of the Literature FIORINO DIGREGORIO, MD RONALD J. BARR, MD DAVID F. FRETZIN, MD
Two patients are reported with pleomorphic lipoma, a benign subcutaneous fatty tumor showing atypia in which histologic diagnosis may be difficult. The tumors are well circumscribed lesions, most commonly occurring in the neck and shoulder of middle aged men. An important histologic criteria is the presence of floret-like multinucleated giant cells embedded in a myxoid stroma. Pleomorphic lipoma may be confused with several malignant soft-tissue neoplasms, including myxoid malignant fibrous histiocytoma and variants of liposarcoma. It is important to establish the correct diagnosis to avoid unnecessary radical surgery. J Dermatol Surg Oncol 1992;18:197-202.
R
ecognition of pseudosarcomatous tumors of adipose tissue with characteristic clinical and histologic features is important to avoid radical ,surgical procedures. In 1977, pleomorphic lipoma was described as a benign tumor simulating a sarcoma.' It is characterized by its location on the neck or shoulder region of middle aged men and histologicallyby its scattered atypical multinucleated giant cells.l-' Our experience with pleomorphic lipoma in two patients and its differentiation from myxoid malignant fibrous histiocytoma and liposarcoma prompted us to report these patients and review the literature.
Materials and Methods Two skin biopsy specimens that showed histologic features of pseudosarcomatous tumors of adipose tissue were studied. Case 1 was from the Department of Pathology of Michael Reese Medical Center, Chicago and Case 2 came from the DermatopathologyLaboratory, University of California, Irvine. Sections from the specimens were fixed in formalin, From the Department of Pathology O F F , FMD), Humana Hospital Michael Reese, Chicago, Illinois, and the Departments of Pathology and Dermatology (RIB), University of California-Zrvine, Zrvine, California. Address correspondence and reprint requests to: David F. Fretzin, MD, Humana Hospital -Michael Reese, 2929 South Ellis, Chicago, ZL 606163390.
0 1992 by Elsevier Science Publishing Co., lnc. 0148-0812/92/$5.00
processed by vacuum infiltration processor and embedded in paraffin. Four-micron sections were cut and stained with hematoxylin and eosin. Clinical information and follow-up were obtained about both lesions from the referring physicians.
Case Reports Case I A 56-year-old black man presented with a mass on his left shoulder that grew slowly to the size of a golf ball. The lesion was incisionally biopsied and later excised. His past medical history includes diabetes mellitus, hypertension, two prior myocardial infarctions, congestive heart failure, chronic renal insufficiency, and bilateral hip replacement. An incisional biopsy provided a 1-cm specimen. Histologic examination showed the epidermis and superficial dermis to be normal. There was an infiltrating tumor in the deep dermis and subcutaneous tissue (Figure 1A and 1B).The tumor showed scattered atypical giant cells with large, hyperchromatic nuclei and spindle-shaped cells in a myxoid background (Figure 2). Most giant cells were multinucleated and some had their nuclei arranged in a floret-like pattern (Figure 3). A variety of inflammatory cells including lymphocytes, histiocytes, eosinophils, neutrophils, plasma cells, and mast cells were present within the tumor. Mitoses were rare (1per 50 high power fields) and lipoblasts were not appreciated. On subsequent excision, a residual 1-cm tumor nodule showed similar histologic features. The final diagnosis was pleomorphic lipoma. In our opinion the differential diagnosis included myxoid malignant fibrous histiocytoma. There has been no recurrence after 26 months. Case 2 A 46-year-old white man presented in 1981 with a subcutaneous lesion on the right side of the forehead of unknown duration. The patient was otherwise healthy. The clinical diagnosis was a lipoma and the lesion was completely excised. The gross specimen contained a 1-cm tumor nodule.
197
DIGREGORIO ET AL 199 PLEOMORPHIC LIPOMA
] Dermatol Surg Oncol 1992;18:197-202
Table 1. Review of 65 Reported Cases of Phleomorphic Lipoma Sex References
M
F
Mean AQe Years maige)
Azzopardi et a15 Bryant'O Bryants Fechner" Nigro et a19 Sakas" Shmookler and Enzinger' Walker and Jones2* DiGregorio et a1 Totals
7 1 1 1 0 1 40 0 2 53
2 0 0 0 1 0 8 1 0 12
59 (41-79) 54 60 52 89 54 57 (30-80) 79 51 (46-56) 56
Mean Duration Years mange)
Mean Greatest Diameter cm (Range)
5 (?-20) 2 1 1 0.67 3 4t (0.17-20)
5.2 (1 - 10) 1 .o 1.9 2.0 3.0 2.5 4.6(0.8-12) 6.0 1.5 (1.0-2.0) 4.3
?
0.5(0.5-?) 3.3
Location Neck
Shoulder
Other'
3 0 0 1 0 1 24 0 0 29
0 0 0 0 0 0 7 0 1 8
6 1 1 0 1 0 17 1 1 28
Back 6, lower extremity 7, head 4, face 4, upper extremity 4, nxilla 2 chest 1.
t Median duration.
however, Azzopardi et a15believe the lesion may be more common than the literature suggests. The male :female ratio is approximately 4 : 1. The usual age of onset is between 50 - 70 years with a mean of 56 years. The average duration of the lesion prior to diagnosis is 3.3 years. Pleomorphic lipoma presents as an asymptomatic, palpable mass; however, occasional lesions may be tender to palpation.' It usually involves the subcutaneous tissue of the neck (45%) or shoulder (l2Y0).',~,'Two cases of pleomorphic lipoma in sites other than the subcutis have been described, one within the muscle of the thigh, and another involving the Lesions vary in size from 1 to 12 cm, with an average size of 4.3 cm. Pleomorphic lipoma is usually a circumscribed, sometimes lobulated, soft tumor with a variable yellow-togrey s u r f a ~ e . ~ - ~ The * *mesenchymal -~ components consist of adipose and myxoid tissue with an admixture of collagen bundles. The amount of these components varies from lesion to lesion and within the same lesion. The collagen bundles appear thick and dense and are more abundant than in ordinary l i p ~ m a s . The ~ - ~cellular ~ portion is usually associated with the collagenous and myxoid areas rather than the mature fat. The tumor cells are dispersed singly and haphazardly throughout the lesion.'~~ Giant cells are either multinucleated (floret-like and nonfloret type) or contain a single large nucleus. The floret-like multinucleated cells have moderate amounts of eosinophilic cytoplasm and multiple, marginally placed, and often overlapping nuclei: "like the petals on a flower."' Many tumor cells are small and ovoid with a single hyperchromatic nucleus.6 Mitoses are rare or abAn atypical sent but when present may be atypi~al.',~J~ mitosis is asymmetrical or multipolar and results in the unequal number of chromosomes in the nuclei of daughter cells. Lipoblasts are also rare, but may be noted in approximately 5090 of cases.5 Vascularity is inconspicuous, consisting of a few thick-walled, often hyalinized
medium- to small-sized blood vessels.' A majority of lesions show a patchy inflammatory infiltrate of lymphocytes and plasma cells, either in a diffuse or perivascular location with variable numbers of mast cells and macrophages.'~~Necrosis is not seen. About 2590 of these tumors have foci of spindle cell differentiation similar to those seen in spindle cell l i p ~ m a . ~ , ' * ~ J ~ Enzinger and Weiss3have suggested a relationship between pleomorphic and spindle cell lipomas. Both have similar clinical presentations; however, pleomorphic lipoma has scattered atypical multinucleated giant cells, a histologic feature not characteristic of spindle cell lipoma (Table 2). Case 1illustrates the typical clinical and histologic features for pleomorphic lipoma, but with involvement of the dermis. This is an unusual but not unique finding.9 The tumor is usually circumscribed; however, in this case the lesion also appears infiltrating. In addition, the inflammatory infiltrate includes eosinophils, which has not been previously described. Case 2 also presents a characteristic histologic appearance; however, the location is in the forehead. Beham et all3reported immunohistochemical staining as negative for MAC-387, fibronectin, laminin, and type IV collagen in the spindle cells, pleomorphic cells, and floret cells of pleomorphic lipoma.13This would tend to negate a histiocytic (negative MAC 387) and prelipoblastic (absence of a basal lamina by negative fibronectin, laminin, and type IV collagen) origin for these cells. Some pleomorphic cells and floret-like multinucleated cells were weakly positive for SlOO protein. This appeared to be a nonspecific finding because the nucleus did not stain, a finding not supportive of a neurogenic Pleomorphic lipoma would appear to be an admixture of mature adipose cells and undifferentiated mesenchymal cells lacking ability to store fat.13J5J6 The differential diagnosis of pleomorphic lipoma in-
J Dermatol Surg Oncol
200 DIGREGORIO ET AL
1992;18:197- 202
Table 2. Comparison of Pleomorphic and Spindle Cell L i p ~ m a ' ~ ~ ~ ' ~ ~ J ~ PI eomorp hic Lipoma Age (years) Male : female ratio Common location
50-70 4:l Neck or shoulder region; subcutaneous
Signs/symptoms
Circumscribed, painless mass, usually several years duration Lipocytes; variable amounts of spindle cells lacking atypia; myxoid areas; thick collagen bundles; inconspicous vasculature; floret-like multinucleated giant cells; some cells with single large hyperchromaticnucleus; mitoses are rare to absent, sometimes atypical; lipoblasts are rare, usually absent; chronic inflammatory cell infiltrate.
Histology
cludes benign and malignant soft tissue tumors. Evans et al reviewed 30 cases classified as well-differentiated liposarcoma from the Mayo Clinic. Of nine lesions located in the subcutaneous tissue, none recurred after excision. They relabeled them atypical lipoma. This lesion is primarily made up of mature adipose tissue with areas of myxoid and/or fibrous tissue including some cells with enlarged atypical nuclei. Multinucleated cells of the floret type may be seen. Kindblom et all8described nine cases of atypical lipoma which involved only the subcutis. Five of these cases recurred. The recurrences may be related to the type of surgical treatment because they were originally diagnosed and treated as ordinary lipomas without surgical margin^.^ Azumi et all9 reviewed 111 cases of atypical or malignant lipomatous lesions. Seventeen were designated differentiated fatty tumors of the somatic soft tissue with atypia. Follow-up evaluation in seven cases showed no recurrence. Pleomorphic and atypical lipoma appear to have overlapping clinical and histologic features. Along with the characteristic clinical setting, Enzinger' stresses floretlike multinucleated giant cells and thick collagen bundles as indicators of a benign behavior. Evans et all7 suggest the subcutaneous location and sharp circumscription are better indicators of a benign behavior in this group of lesions. However, Enzinger and Weiss3suggest cautious use of the term "atypical lipoma." The tumor has the same histologic appearance as a liposarcoma in the retroperitoneum, but diagnosis is based on clinical location. The recurrence rate of atypical lipoma is higher than benign lipomas that include pleomorphic and spindle cell lipomas. Enzinger and Weiss recommend atypical lipoma, pleomorphic lipoma, and spindle cell lipoma be kept as separate entities. The most critical differential diagnosis for pleomorphic lipoma is a malignant sarcoma, either myxoid malig-
''
Spindle Cell Lipoma 45 - 65 9:1 Posterior neck or shoulder region; subcutaneous Solitary, painless firm nodule, usually several years duration. Lipocytes; spindle cells lacking atypia; myxoid areas; variable amounts of dense collagen bundles, usually few; inconspicuous vasculature.
nant fibrous histiocytoma or liposarcoma (Table 3). Malignant fibrous histiocytoma is the most common soft tissue sarcoma of adult life.3 These tumors primarily involve the deeper soft tissue.20The most common site of involvement is the thigh and buttock whereas pleomorphic lipoma usually involves the more superficial subcutaneous tissue of the neck and shoulder region. Histologically, areas of myxoid malignant fibrous histiocytoma may closely resemble a pleomorphic lipoma. However, careful analysis of the former will usually show more cellular areas exhibiting a characteristic storiform pattern, a conspicuous vasculature, greater degree of nuclear pleomorphism, and numerous m i t o s e ~ . ~ , ~ * ~ J ~ Liposarcoma is commonly located in the retroperitoneum and thigh, usually within muscle or deep soft tis~ u e . ~ The * ~ Owell-differentiated sclerosing type may have microscopic areas similar to pleomorphic lipoma. Intermixed dense collagen bundles and floret-like multinucleated giant cells may be seen.5However, areas of fibrosis show a predominately uniform network of delicate collagen fibrils and lipoblasts are more frequently seen than floret-like multinucleated giant cell^.^-^*^ Myxoid liposarcoma usually has sheet-like areas with lipoblasts in a background stoma showing a rich capillary network and myxoid material. Multinucleated giant cells are rare. Pleomorphic liposarcoma shows sheet-like areas of tumor cells with prominent atypia, readily identified lipoblasts, mitoses, necrosis, and h e m ~ r r h a g e . ~ - ~ Surgical excision is the mode of therapy for pleomorphic lipoma. Simple enucleation and blunt dissection have been d e s ~ r i b e d . ~ ,Simple ~ , ~ ' local excision of the tumor with clear margins provides excellent results for cure.3Radical deforming surgery must not be considered for pleomorphic lipoma. Follow-up data are available in 72% (47/65) of cases reported to date.4,5,8,9J0*21 The duration ranges from 0.5 to
DIGREGORIO ET AL PLEOMORPHIC LIPOMA
Dermatol Surg Oncol 1992;18:197- 202
201
Table 3. Myxoid Malignant Fibrous Histiocytoma and Variants of Liposarcoma Considered in Differential Diagnosis of Pleomorphic L i p o m ~ ~ , ~ , Z ~ Myxoid Malignant Fibrous Histiocytoma
.
Variants of Liposarcoma
Age (yeas) Male :female ratio
50-70 2:l
Common location
Skeletal muscle of extremities retroperitoneum Extremities: painless, enlarging mass of several months duration. Retroperitoneum: anorexia, malaise, weight loss, increased abdominal, pressure.
Signs/symptoms
Histology
Myxoid areas; cellular areas exhibit characteristicstoriform pattern, high degree of nuclear pleomorphism, multinucleation; numerous mitoses; conspicuous vascular pattern; chronic inflammatory cells.
13.5 years. With one exception, there has been no recurrence of a pleomorphic lipoma.' This one exception allegedly represents the fourth local recurrence, but previously lesions had been excised in Africa and the nature of the surgeries and histology is uncertain.
2.
3.
Summary
4.
Experience with two cases of subcutaneous fatty tumors with atypia illustrates the difficulty in there diagnosis. Knowledge of the characteristic clinical and histologic features of pleomorphic lipoma should help to differentiate this benign pseudosarcomatous tumor from malignant sarcomas. Because pleomorphic lipoma presents as a visible superficial subcutaneous mass it is important that the dermatologist and dermatopathologist be familiar with it. Establishing the correct diagnosis will prevent unwarranted deforming surgery.
8.
References
9.
1. Enzinger FM. Benign lipomatous tumors simulating a sarcoma. In: Management of Primary Bone and Soft Tissue
5.
6. 7.
45 - 60 1:l to2:l Retroperitoneum:favors females Skeletal muscle of thigh; retroperitoneum
Extremities:ill-defined, insiduously growing, deep mass of variable duration (several months- years) Retroperitoneum: increasing abdominal girth, weight loss, abdominal pain, anorexia. Well differentiated sclerosing type: lipocytes; areas of fibrosis showing uniform network of delicate collagen fibrils, atypical cells with hyperchromatic nucleus, occasional lipoblasts, rare multinucleated cells; sparse dense collagen bundles. Myxoid Type: sheet-like areas of lipoblasts in a background showing a rich capillary network and myxoid material; rare multinucleated giant cells; mitoses are rare or absent. Pleomorphic Type: sheet-like areas of tumor cells showing prominent nuclear pleomorphism, some large and bizarre; lipoblasts and mitoses are easily found; necrosis and hemorrhage.
Tumors. Chicago: Year Book Medical Publishers, 1977:ll24. Bednar B, Mirejovsky P. Histogenesis of benign pleomorphic mesenchymal tumors. Czechoslov Med 1988;ll: 81-5. Enzinger FM, Weiss SW. Soft tissue tumors, 2nd ed. St. Louis: CV Mosby, 1988:269-382. Shmookler BM, Enzinger FM. Pleomorphic lipoma: a benign tumor simulating liposarcoma. Cancer 1981;47: 126-33. Azzopardi JG, Iocco J, Salm R. Pleomorphic lipoma: a tumor simulating liposarcoma. Histopathology 1983;7 511-23. Cason JD, Seidman I, Lusskin R. Intramuscular pleomorphic lipoma, (letter). NY State J Med 1986;86:657-8. Guillou L, Dehon A, Charlin B, Madarnas P. Pleomorphic lipoma of the tongue: case report and literature review. J Otolaryngol 1986;15:3 13- 6. Bryant J. Pleomorphic lipoma of the bulbar conjunctiva. Ann Ophthalmol 1981;19:148- 9. Nigro MA, Chieregato GC, Querci Della Rovere G.Pleomorphic lipoma of the dermis. Br J Dermatol 1987;116: 713-17.
202 DIGREGORIO ET AL
Dermatol Surg Oncol 1992;18:197- 202
10. Bryant J. A pleomorphic lipoma in the scalp. J Dermatol Surg Oncol 1981;7:323-5. 1 1 . Sakas EL. Case for diagnosis: pleomorphic lipoma. Milit Med 1982;147:61, 73. 12. Enzinger FM, Harvey DA. Spindle cell lipoma. Cancer 1975;36:1852-9. 13. Beham A, Schmid C, Hod1 S, Fletcher CDM. Spindle cell and pleomorphic lipoma: an immunohistochemical study and histogenetic analysis. J Pathol 1989;158:219-22. 14. Kamino H, Yu-Yun Lee J, Berke A. Pleomorphic fibroma of the skin: a benign neoplasm with cytologic atypia. Am J Surg Pathol 1989;13:107-13. 15. Bolen JW, Thorning D. Spindle cell lipoma. A clinical, lightand electron-microscopical study. Am J Surg Pathol 1981;5:435 -41. 16. Knipping G, Popper H. Composition of fat in different types of liposarcomas in comparison with lipomas. Cancer Lett 1989;46:51-6.
17. Evans HL, Soule EH, Wilkelmann RK. Atypical lipoma, typical intramuscular lipoma and well differentiated retroperitoneal liposarcoma; a reappraisal of 30 cases formerly classified as well differentiated liposarcoma. Cancer 1979;43:574 - 84. 18. Kindblom LG, Angerwall L, Fassina AS. Atypical lipoma. Acta Pathol Microbiol Immunol Scand Sect A Pathol 1982;90:27-36. 19. Azumi N, Curtis J, Kempson RL, Hendrickson MR. Atypical and malignant neoplasms showing lipomatous differentiation. Am J Surg Pathol 1987;11:161-83. 20. Lever WF, Schaumberg-Lever G. Histoathology of the skin, 7th ed. Philadelphia: JB Lippincott. 1990;724-8. 21. Fechner RE. Pathologic Quiz Case 1. Pleomorphic lipoma. Arch Otolaryngol 1984;110:820-22. 22. Walker AN, Jones PF. Pathologic Quiz Case 2. Pleomorphic lipoma. Arch Otolaryngol Head & Neck Surg 1986;112: 568-9.
Two patients are reported with pleomorphic lipoma, a benign subcutaneous fatty tumor showing atypia in which histologic diagnosis may be difficult. The tumors are well circumscribed lesions, most commonly occurring in the neck and shoulder of middle aged men. An important histologic criteria is the presence of floret-like multinucleated giant cells embedded in a myxoid stroma. Pleomorphic lipoma may be confused with several malignant soft-tissue neoplasms, including myxoid malignant fibrous histiocytoma and variants of liposarcoma. It is important to establish the correct diagnosis to avoid unnecessary radical surgery. J Dermatol Surg Oncol 1992;18:197-202.
R
ecognition of pseudosarcomatous tumors of adipose tissue with characteristic clinical and histologic features is important to avoid radical ,surgical procedures. In 1977, pleomorphic lipoma was described as a benign tumor simulating a sarcoma.' It is characterized by its location on the neck or shoulder region of middle aged men and histologicallyby its scattered atypical multinucleated giant cells.l-' Our experience with pleomorphic lipoma in two patients and its differentiation from myxoid malignant fibrous histiocytoma and liposarcoma prompted us to report these patients and review the literature.
Materials and Methods Two skin biopsy specimens that showed histologic features of pseudosarcomatous tumors of adipose tissue were studied. Case 1 was from the Department of Pathology of Michael Reese Medical Center, Chicago and Case 2 came from the DermatopathologyLaboratory, University of California, Irvine. Sections from the specimens were fixed in formalin, From the Department of Pathology O F F , FMD), Humana Hospital Michael Reese, Chicago, Illinois, and the Departments of Pathology and Dermatology (RIB), University of California-Zrvine, Zrvine, California. Address correspondence and reprint requests to: David F. Fretzin, MD, Humana Hospital -Michael Reese, 2929 South Ellis, Chicago, ZL 606163390.
0 1992 by Elsevier Science Publishing Co., lnc. 0148-0812/92/$5.00
processed by vacuum infiltration processor and embedded in paraffin. Four-micron sections were cut and stained with hematoxylin and eosin. Clinical information and follow-up were obtained about both lesions from the referring physicians.
Case Reports Case I A 56-year-old black man presented with a mass on his left shoulder that grew slowly to the size of a golf ball. The lesion was incisionally biopsied and later excised. His past medical history includes diabetes mellitus, hypertension, two prior myocardial infarctions, congestive heart failure, chronic renal insufficiency, and bilateral hip replacement. An incisional biopsy provided a 1-cm specimen. Histologic examination showed the epidermis and superficial dermis to be normal. There was an infiltrating tumor in the deep dermis and subcutaneous tissue (Figure 1A and 1B).The tumor showed scattered atypical giant cells with large, hyperchromatic nuclei and spindle-shaped cells in a myxoid background (Figure 2). Most giant cells were multinucleated and some had their nuclei arranged in a floret-like pattern (Figure 3). A variety of inflammatory cells including lymphocytes, histiocytes, eosinophils, neutrophils, plasma cells, and mast cells were present within the tumor. Mitoses were rare (1per 50 high power fields) and lipoblasts were not appreciated. On subsequent excision, a residual 1-cm tumor nodule showed similar histologic features. The final diagnosis was pleomorphic lipoma. In our opinion the differential diagnosis included myxoid malignant fibrous histiocytoma. There has been no recurrence after 26 months. Case 2 A 46-year-old white man presented in 1981 with a subcutaneous lesion on the right side of the forehead of unknown duration. The patient was otherwise healthy. The clinical diagnosis was a lipoma and the lesion was completely excised. The gross specimen contained a 1-cm tumor nodule.
197
DIGREGORIO ET AL 199 PLEOMORPHIC LIPOMA
] Dermatol Surg Oncol 1992;18:197-202
Table 1. Review of 65 Reported Cases of Phleomorphic Lipoma Sex References
M
F
Mean AQe Years maige)
Azzopardi et a15 Bryant'O Bryants Fechner" Nigro et a19 Sakas" Shmookler and Enzinger' Walker and Jones2* DiGregorio et a1 Totals
7 1 1 1 0 1 40 0 2 53
2 0 0 0 1 0 8 1 0 12
59 (41-79) 54 60 52 89 54 57 (30-80) 79 51 (46-56) 56
Mean Duration Years mange)
Mean Greatest Diameter cm (Range)
5 (?-20) 2 1 1 0.67 3 4t (0.17-20)
5.2 (1 - 10) 1 .o 1.9 2.0 3.0 2.5 4.6(0.8-12) 6.0 1.5 (1.0-2.0) 4.3
?
0.5(0.5-?) 3.3
Location Neck
Shoulder
Other'
3 0 0 1 0 1 24 0 0 29
0 0 0 0 0 0 7 0 1 8
6 1 1 0 1 0 17 1 1 28
Back 6, lower extremity 7, head 4, face 4, upper extremity 4, nxilla 2 chest 1.
t Median duration.
however, Azzopardi et a15believe the lesion may be more common than the literature suggests. The male :female ratio is approximately 4 : 1. The usual age of onset is between 50 - 70 years with a mean of 56 years. The average duration of the lesion prior to diagnosis is 3.3 years. Pleomorphic lipoma presents as an asymptomatic, palpable mass; however, occasional lesions may be tender to palpation.' It usually involves the subcutaneous tissue of the neck (45%) or shoulder (l2Y0).',~,'Two cases of pleomorphic lipoma in sites other than the subcutis have been described, one within the muscle of the thigh, and another involving the Lesions vary in size from 1 to 12 cm, with an average size of 4.3 cm. Pleomorphic lipoma is usually a circumscribed, sometimes lobulated, soft tumor with a variable yellow-togrey s u r f a ~ e . ~ - ~ The * *mesenchymal -~ components consist of adipose and myxoid tissue with an admixture of collagen bundles. The amount of these components varies from lesion to lesion and within the same lesion. The collagen bundles appear thick and dense and are more abundant than in ordinary l i p ~ m a s . The ~ - ~cellular ~ portion is usually associated with the collagenous and myxoid areas rather than the mature fat. The tumor cells are dispersed singly and haphazardly throughout the lesion.'~~ Giant cells are either multinucleated (floret-like and nonfloret type) or contain a single large nucleus. The floret-like multinucleated cells have moderate amounts of eosinophilic cytoplasm and multiple, marginally placed, and often overlapping nuclei: "like the petals on a flower."' Many tumor cells are small and ovoid with a single hyperchromatic nucleus.6 Mitoses are rare or abAn atypical sent but when present may be atypi~al.',~J~ mitosis is asymmetrical or multipolar and results in the unequal number of chromosomes in the nuclei of daughter cells. Lipoblasts are also rare, but may be noted in approximately 5090 of cases.5 Vascularity is inconspicuous, consisting of a few thick-walled, often hyalinized
medium- to small-sized blood vessels.' A majority of lesions show a patchy inflammatory infiltrate of lymphocytes and plasma cells, either in a diffuse or perivascular location with variable numbers of mast cells and macrophages.'~~Necrosis is not seen. About 2590 of these tumors have foci of spindle cell differentiation similar to those seen in spindle cell l i p ~ m a . ~ , ' * ~ J ~ Enzinger and Weiss3have suggested a relationship between pleomorphic and spindle cell lipomas. Both have similar clinical presentations; however, pleomorphic lipoma has scattered atypical multinucleated giant cells, a histologic feature not characteristic of spindle cell lipoma (Table 2). Case 1illustrates the typical clinical and histologic features for pleomorphic lipoma, but with involvement of the dermis. This is an unusual but not unique finding.9 The tumor is usually circumscribed; however, in this case the lesion also appears infiltrating. In addition, the inflammatory infiltrate includes eosinophils, which has not been previously described. Case 2 also presents a characteristic histologic appearance; however, the location is in the forehead. Beham et all3reported immunohistochemical staining as negative for MAC-387, fibronectin, laminin, and type IV collagen in the spindle cells, pleomorphic cells, and floret cells of pleomorphic lipoma.13This would tend to negate a histiocytic (negative MAC 387) and prelipoblastic (absence of a basal lamina by negative fibronectin, laminin, and type IV collagen) origin for these cells. Some pleomorphic cells and floret-like multinucleated cells were weakly positive for SlOO protein. This appeared to be a nonspecific finding because the nucleus did not stain, a finding not supportive of a neurogenic Pleomorphic lipoma would appear to be an admixture of mature adipose cells and undifferentiated mesenchymal cells lacking ability to store fat.13J5J6 The differential diagnosis of pleomorphic lipoma in-
J Dermatol Surg Oncol
200 DIGREGORIO ET AL
1992;18:197- 202
Table 2. Comparison of Pleomorphic and Spindle Cell L i p ~ m a ' ~ ~ ~ ' ~ ~ J ~ PI eomorp hic Lipoma Age (years) Male : female ratio Common location
50-70 4:l Neck or shoulder region; subcutaneous
Signs/symptoms
Circumscribed, painless mass, usually several years duration Lipocytes; variable amounts of spindle cells lacking atypia; myxoid areas; thick collagen bundles; inconspicous vasculature; floret-like multinucleated giant cells; some cells with single large hyperchromaticnucleus; mitoses are rare to absent, sometimes atypical; lipoblasts are rare, usually absent; chronic inflammatory cell infiltrate.
Histology
cludes benign and malignant soft tissue tumors. Evans et al reviewed 30 cases classified as well-differentiated liposarcoma from the Mayo Clinic. Of nine lesions located in the subcutaneous tissue, none recurred after excision. They relabeled them atypical lipoma. This lesion is primarily made up of mature adipose tissue with areas of myxoid and/or fibrous tissue including some cells with enlarged atypical nuclei. Multinucleated cells of the floret type may be seen. Kindblom et all8described nine cases of atypical lipoma which involved only the subcutis. Five of these cases recurred. The recurrences may be related to the type of surgical treatment because they were originally diagnosed and treated as ordinary lipomas without surgical margin^.^ Azumi et all9 reviewed 111 cases of atypical or malignant lipomatous lesions. Seventeen were designated differentiated fatty tumors of the somatic soft tissue with atypia. Follow-up evaluation in seven cases showed no recurrence. Pleomorphic and atypical lipoma appear to have overlapping clinical and histologic features. Along with the characteristic clinical setting, Enzinger' stresses floretlike multinucleated giant cells and thick collagen bundles as indicators of a benign behavior. Evans et all7 suggest the subcutaneous location and sharp circumscription are better indicators of a benign behavior in this group of lesions. However, Enzinger and Weiss3suggest cautious use of the term "atypical lipoma." The tumor has the same histologic appearance as a liposarcoma in the retroperitoneum, but diagnosis is based on clinical location. The recurrence rate of atypical lipoma is higher than benign lipomas that include pleomorphic and spindle cell lipomas. Enzinger and Weiss recommend atypical lipoma, pleomorphic lipoma, and spindle cell lipoma be kept as separate entities. The most critical differential diagnosis for pleomorphic lipoma is a malignant sarcoma, either myxoid malig-
''
Spindle Cell Lipoma 45 - 65 9:1 Posterior neck or shoulder region; subcutaneous Solitary, painless firm nodule, usually several years duration. Lipocytes; spindle cells lacking atypia; myxoid areas; variable amounts of dense collagen bundles, usually few; inconspicuous vasculature.
nant fibrous histiocytoma or liposarcoma (Table 3). Malignant fibrous histiocytoma is the most common soft tissue sarcoma of adult life.3 These tumors primarily involve the deeper soft tissue.20The most common site of involvement is the thigh and buttock whereas pleomorphic lipoma usually involves the more superficial subcutaneous tissue of the neck and shoulder region. Histologically, areas of myxoid malignant fibrous histiocytoma may closely resemble a pleomorphic lipoma. However, careful analysis of the former will usually show more cellular areas exhibiting a characteristic storiform pattern, a conspicuous vasculature, greater degree of nuclear pleomorphism, and numerous m i t o s e ~ . ~ , ~ * ~ J ~ Liposarcoma is commonly located in the retroperitoneum and thigh, usually within muscle or deep soft tis~ u e . ~ The * ~ Owell-differentiated sclerosing type may have microscopic areas similar to pleomorphic lipoma. Intermixed dense collagen bundles and floret-like multinucleated giant cells may be seen.5However, areas of fibrosis show a predominately uniform network of delicate collagen fibrils and lipoblasts are more frequently seen than floret-like multinucleated giant cell^.^-^*^ Myxoid liposarcoma usually has sheet-like areas with lipoblasts in a background stoma showing a rich capillary network and myxoid material. Multinucleated giant cells are rare. Pleomorphic liposarcoma shows sheet-like areas of tumor cells with prominent atypia, readily identified lipoblasts, mitoses, necrosis, and h e m ~ r r h a g e . ~ - ~ Surgical excision is the mode of therapy for pleomorphic lipoma. Simple enucleation and blunt dissection have been d e s ~ r i b e d . ~ ,Simple ~ , ~ ' local excision of the tumor with clear margins provides excellent results for cure.3Radical deforming surgery must not be considered for pleomorphic lipoma. Follow-up data are available in 72% (47/65) of cases reported to date.4,5,8,9J0*21 The duration ranges from 0.5 to
DIGREGORIO ET AL PLEOMORPHIC LIPOMA
Dermatol Surg Oncol 1992;18:197- 202
201
Table 3. Myxoid Malignant Fibrous Histiocytoma and Variants of Liposarcoma Considered in Differential Diagnosis of Pleomorphic L i p o m ~ ~ , ~ , Z ~ Myxoid Malignant Fibrous Histiocytoma
.
Variants of Liposarcoma
Age (yeas) Male :female ratio
50-70 2:l
Common location
Skeletal muscle of extremities retroperitoneum Extremities: painless, enlarging mass of several months duration. Retroperitoneum: anorexia, malaise, weight loss, increased abdominal, pressure.
Signs/symptoms
Histology
Myxoid areas; cellular areas exhibit characteristicstoriform pattern, high degree of nuclear pleomorphism, multinucleation; numerous mitoses; conspicuous vascular pattern; chronic inflammatory cells.
13.5 years. With one exception, there has been no recurrence of a pleomorphic lipoma.' This one exception allegedly represents the fourth local recurrence, but previously lesions had been excised in Africa and the nature of the surgeries and histology is uncertain.
2.
3.
Summary
4.
Experience with two cases of subcutaneous fatty tumors with atypia illustrates the difficulty in there diagnosis. Knowledge of the characteristic clinical and histologic features of pleomorphic lipoma should help to differentiate this benign pseudosarcomatous tumor from malignant sarcomas. Because pleomorphic lipoma presents as a visible superficial subcutaneous mass it is important that the dermatologist and dermatopathologist be familiar with it. Establishing the correct diagnosis will prevent unwarranted deforming surgery.
8.
References
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1. Enzinger FM. Benign lipomatous tumors simulating a sarcoma. In: Management of Primary Bone and Soft Tissue
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6. 7.
45 - 60 1:l to2:l Retroperitoneum:favors females Skeletal muscle of thigh; retroperitoneum
Extremities:ill-defined, insiduously growing, deep mass of variable duration (several months- years) Retroperitoneum: increasing abdominal girth, weight loss, abdominal pain, anorexia. Well differentiated sclerosing type: lipocytes; areas of fibrosis showing uniform network of delicate collagen fibrils, atypical cells with hyperchromatic nucleus, occasional lipoblasts, rare multinucleated cells; sparse dense collagen bundles. Myxoid Type: sheet-like areas of lipoblasts in a background showing a rich capillary network and myxoid material; rare multinucleated giant cells; mitoses are rare or absent. Pleomorphic Type: sheet-like areas of tumor cells showing prominent nuclear pleomorphism, some large and bizarre; lipoblasts and mitoses are easily found; necrosis and hemorrhage.
Tumors. Chicago: Year Book Medical Publishers, 1977:ll24. Bednar B, Mirejovsky P. Histogenesis of benign pleomorphic mesenchymal tumors. Czechoslov Med 1988;ll: 81-5. Enzinger FM, Weiss SW. Soft tissue tumors, 2nd ed. St. Louis: CV Mosby, 1988:269-382. Shmookler BM, Enzinger FM. Pleomorphic lipoma: a benign tumor simulating liposarcoma. Cancer 1981;47: 126-33. Azzopardi JG, Iocco J, Salm R. Pleomorphic lipoma: a tumor simulating liposarcoma. Histopathology 1983;7 511-23. Cason JD, Seidman I, Lusskin R. Intramuscular pleomorphic lipoma, (letter). NY State J Med 1986;86:657-8. Guillou L, Dehon A, Charlin B, Madarnas P. Pleomorphic lipoma of the tongue: case report and literature review. J Otolaryngol 1986;15:3 13- 6. Bryant J. Pleomorphic lipoma of the bulbar conjunctiva. Ann Ophthalmol 1981;19:148- 9. Nigro MA, Chieregato GC, Querci Della Rovere G.Pleomorphic lipoma of the dermis. Br J Dermatol 1987;116: 713-17.
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Dermatol Surg Oncol 1992;18:197- 202
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