Path. Res. Pract. 188, 1083-1087 (1992)
Teaching Cases
Giant Cell Granuloma of the
Lung:~
W. W6ckeP, A. Lagemanl, H. Ueberberg2, J. Stumpner3 , H. Suren 4 and H. Mandelkow5 Pathologisches Institut 1, Pneumologische Klinik3, Radiologisches Institut4 und Thoraxchirurgische Abteilung5 des Zentralkrankenhauses Gauting der LVA Oberbayem; Abteilung Experimentelle Pathologie 2, Dr. Karl Thomae GmbH, Biberach an der Riss, FRG
SUMMARY
In a 50-year-old man without bronchopulmonary symptoms a round mass lesion close to the hilum of the right lung was detected in a routine chest x-ray and confirmed by computed tomography. Histological examination of two biopsy specimens did not result in a definitive diagnosis. Therefore thoracotomy with enucleation of the focus was performed. The histological picture of the lesion is characterized by connective tissue proliferation, multinucleated giant cells, ossification, localised hemorrhage, deposits of hemosiderin and foci of foam cells. The findings are interpreted as a giant cell granuloma of the lung.
Introduction Despite knowledge of the clinical status interpretation of histological findings in the bronchial mucosa and transbronchial lung biopsies can be extremely difficult, particularly as only small fragments of tissue material are usually available for examination. We report on tissue alterations not allowing exact diagnosis in the biopsy material. Interpretation of the morphological findings remains problematic in the surgical specimen, especially since we have found only two approximately comparable cases in the literature. Case Report Clinical Data
During a routine examination three weeks prior to admission to our clinic on November 3,1988 a chest x-ray was taken of a male patient born on March 6, 1938. He * Dedicated to Dr. med. habil. V. Haenselt, Bad Berka, on the occasion of his 70th birthday. © 1992 by Gustav Fischer Verlag, Stuttgart
complained of pain in the right shoulder and flush symptoms present for many years. A right suprahilar circular nodule measuring almost 2 em in diameter, projecting into the anterior segment of the upper lobe, was observed. The patient was admitted to hospital with a provisional diagnosis of bronchial carcinoma. On admission the patient gave no history of productive or non-productive cough, shortness of breath, loss of weight or night sweats. He had not smoked for 13 years but prior to that he had smoked 40 cigarettes per day. There had been no antecedent illnesses, apart from surgery for a right inguinal hernia and the incision of anal abscesses 30 years previously. Clinical Findings
On admission the patient measuring 1.75 m and weighing 95 kg presented neither cyanosis nor edema, and there were no lymph nodes palpable. Grade II goitre was present. No abnormalities were detected on percussion and' auscultation of the heart and lungs, B.P. was l40/105 mmlHg and pulse rate 96 beats per min. No abnormality was found on abdominal palpation. A herniotomy scar was present in the right inguinal regIOn. 0344-0338/92/0188-1083 $3.50/0
1084 . W. Wackel et al.
Laboratory Values
Serum uric acid was 7.5 mgldl and gamma GT was 30 Uli. Values for all other routine laboratory tests were normal. Urinary excretion of calcium and serum parathyroid hormone were normal. Two microscopic and cultural investigations of bronchial secretions for tubercle bacilli were negative. The tuberculin test was positive with 10 TU. Radiological Findings
Chest x-rays showed a localised polycyclic density close to the hilum of the right lung, presumably lying in the anterior segment of the upper lobe. Computed tomography (Fig. 1) revealed a homogeneous and calcified round focus (120 HE) measuring 1.7 cm in diameter.
Surgical Findings
A hard, well defined nodule with an irregular surface was palpable close to the hilum in the anterior segment of the right upper lobe. Complete removal was possible. Other intrathoracic findings were normal, in particular no enlarged lympq nodes were detected. The postoperative course was uneventful. Morphological Findings
Biopsies of the bronchial mucosa (E 4260/88 and 4305/88) and surgical specimens (E 4506/88) were stained: Hematoxylin and Eosin, Elastica van Gieson, Berlin blue. The lesion consists of a proliferation of connective tissue containing a variable number of cellular elements. The majority are spindle cells in interlacing rows arranged in a disorderly fashion. Collagen fibres are scattered between the cells. In cellular areas the nuclei appear somewhat polymorphous. Some nucleoli are enlarged and numerous multinuclear giant cells were present behveen the proliferating fibroblast-like cells (Fig. 2). There were many irreg-
Fig. 1. Computed tomography: homogeneous and calcified round focus (H & E, 120) 1.7 em in diameter.
Further Investigations
No abnormalities were found in lung function tests, ECG at rest and under exercise with submaximal effort to 60 W, bone scintigraphy and upper abdominal sonography. Rigid bronchoscopy was performed under general anesthesia and muscle relaxation. There were no abnormalities of the epiglottis and vocal cords. The mucous membrane of the normally patent trachea, the carina and the bronchial system of both lungs were normal. All segmental ostia were normal and patent. The anterior segmental bronchus of the right upper lobe divided into three subsegmental bronchi. In the middle subsegmental bronchus there was a round yellowish mass lesion with a smooth surface and hard consistency. Biopsies were taken from this lesion and the adjoining mucous membrane. As no definitive histological diagnosis could be made, righi-sided anterolateral thoracotomy via the sixth intercostal space was performed.
Fig. 2. Particularly cellular area with numerous multinuclear giant cells (H & E, x 25).
Giant Cell Granuloma of the Lung· 1085
Fig. 3. Many irregular spicules of newly formed bone or osteoid tissue, a few of them in contact with the cartilage of the bronchus (Elastica van Gieson, x 10).
Fig. 4. Bone partly surrounded by osteoblasts (H & E, x 50).
ular trabeculae of newly formed bone or osteoid tissue (Fig. 3), partly surrounded by osteoblasts (Fig. 4). Some trabeculae were immediately adjacent to the cartilage of the bronchial wall. In addition ·focal hemorrhage and siderotic deposits were present in several areas. Occasionally there were small groups of foam cells. Around lacunae caused by the dissolution of cholesterol crystals, foreign body giant cells were present and in one area closely arranged, dilated thin-walled blood vessels were seen (Fig. 6).
exact diagnosis thoracotomy with enucleation of the focus was performed. The histological picture of the excised lesion was characterized by a proliferation of connective tissue, multinucleated giant cells and ossification corresponding to the calcification in the computed tomogram; localized hemorrhage, deposits of hemosiderin and foci of foam cells. The exact interpretation of this process was not possible from the biopsy material alone and even now remains problematic as only two approximately similar cases have been reported in the literature 2, 6. One case described two fused osteoclastoma-like giant cell tumors in the upper lobe of the left lung in a forty-year-old man. Histological confirmation of the diagnosis was obtained by lobectomy. The important difference in the described tumor was the lack of ossification. Interpretation of the findings in the other case report was difficult as it was published in Polish6 . There was no doubt that there was a proliferation of multinuclear giant cells, ossification and focal calcification. The histological findings in our case were most likely compatible with a giant cell granuloma
Discussion In this 50-year-old patient without bronchopulmonary symptoms a round mass lesion close to the hilum of the right lung was detected in a chest x-ray taken during a routine examination. The focus was confirmed by computed tomography and shown to be calcified. There was no indication of the nature of the nodule. As the histological investigation of two biopsy specimens did not result in
1086 . W. Woekel et al.
Fig.S. Aggregates of so-called foam cells (H & E, x 50).
Fig. 6. Area of closely arranged dilated thin-walled blood vessels (H & E, x 25) .
which until recently was known to occur mainly in the mandible 4 and other cranial bones l . The differential diagnosis included a giant cell tumor (osteoclastoma), as it presents in other regions of the skeletons. Only recently it has been reported that apart from the osseous system "giant cell tumors" also occur in the larynx 3 . Eight such cases are to be found in the AFIPOTR-material. The ages of these patients ranged from the second to the seventh decades and males and females were equally affected. Metastases were absent in all of these cases. Occasionally laryngectomy was necessary due to the size of the tumor causing airway obstruction. The histological picture corresponded in some cases to a true giant cell tumor of bone and in other cases to a giant cell granuloma of the facial bones. Because of the prominent vascular pattern in the histological findings in two cases, these were similar to those of an aneurysmal bone cyst. The histological findings in our case therefore correspond to those observed in the larynx. HirschI and Katz I have defined several criteria for differential diagnosis --between giant cell granuloma and giant cell tumor (osteoclastoma). The arrangement of giant
cells in groups around localised hemorrhage, a stroma of oval and spindle-shaped cells with collagen fibres, recent and old hemorrhage with siderotic deposits, small giant cells with numerous irregular nuclei as well as small cells with few nuclei and the formation of osteoid and bone are typical of giant cell granuloma. The giant cell tumor (osteoclastoma) is characterized by a homogeneous distribution of giant cells, a stroma !=omposed predominantly of plump, round or oval cells, slight to moderate hemorrhage with small amounts of hemosiderin, larger giant cells with more nuclei and no ossification. If these differential diagnostic criteria are applied to our case, without taking the completely different organ manifestation into consideration, the findings described in our case are more likely to be those of a giant cell granuloma of the !ung and corresponding with the findings described by Sliwiitska and Iwanik 6 than those of the infrequently occurring pulmonary giant cell tumor mentioned 2 . The fact that an area resembles an aneurysmal bone cyst, as also mentioned by Hyams et aJ.3 is not inconsistent with these findings. The histogenesis of the changes under discussion cannot be answered precisely. Just as in the larynx 3 ossified
Giant Cell Granuloma of the Lung· Letter to the Case· 1087
cartilage as well as connective tissue can be considered as originating in the lungs or the bronchial system. However, further observations are necessary to elucidate this hypothesis. The etiology of this proliferative process is completely obscure. In our opinion it is a reactive rather than a neoplastic process - analogous to the central (reparative) giant cell granuloma of the jaw bone4 . Therefore in contrast to Sliwinska and Iwanik 6 we do not refer to it as a giant cell tumor but prefer to use the term giant cell granuloma.
References 1 HirschI S, Katz A (1974) Giant cell reparative granuloma outside the jaw bone. Diagnostic criteria and review of the
literature with the first case described in the temporal bone. Human Pathol5: 171-181 2 Hofmann D, Jander R, Filler D (1980) Osteoclastoma-like giant cell tumor of the lung. Thorac cardiovasc Surg 28: 444-445 3 Hyams VJ, Batsakis JG, Michaels L (1988) Tumors of the Upper Respiratory Tract and Ear. Atlas of Tumor Pathology. Second Series, Fascicle 25. Armed Forces Institute of Pathology, Washington, D.C. 4 Pindborg Kramer IRH, Torloni H (1971) Histological Typing of Odontogenic Tumours, Jaw Cysts, and Allied Lesions. International Histological Classification of Tumours. No 5. World Health Organization, Geneva 5 Schajowicz F, Ackerman LV, Sis sons HA, Sobin LH, Torloni H (1972) Histological Typing of Bone Tumours. International Histological Classification of Tumours. No 6. World Health Organization, Geneva 6 Sliwinska I, Iwanik J (1975) Guz olbrzymiokomorkowy pluca. Patal pol 26: 535-540
n,
Received October 10, 1989 . Accepted September 19, 1991
Key words: Lung - Giant cell granuloma - Giant cell tumour Prof. Dr. W. Wackel, Pathologisches Institut des Zentralkrankenhauses der LVA Obb., Unterbrunner StralSe 85, D-8035 Gauting, FRG
Letters to the Case D. Dienemann and C.-.A. Hartmann Berlin, FRG
It is true that the lesion described by the authors has a histological similarity with central (reparative) giant cell granuloma of the jawbone (CGCG). However, the histological profile illustrated in this case is not pathognomonic for a particular disease entity, and therefore requires further interpretation according to type and localization of the disease. Thus the histology of brown tumors associ'ated with hyperparathyroidism is nearly identical to that of CGCG, despite a completely different etiology. Since Jaffe traced the origin of CGCG to trauma with progressive hemorrhaging in 1953, which has been demonstrated in a number of instances 4 , CGCG has been interpreted as a reparative product. In the lung there are also morphologically similar transformations which are known under a variety of different names, often called "post-inflammatory tumors" or "inflammatory pseudotumors" 2,3,9,12,13. The cause of these lesions is suspected to be a past case of pneumonia, especially including virus-associated interstitial pneumonia, and the pseudotumor is interpreted as an organiza-
tional product of chronic pneumonia. Several studies 9, 11, 13 have emphasized the heterogeneity of inflammatory pseudotumors, which by no means always have the histological profile of a plasma cell granuloma 1,8, but can have a histiocytoma-like character. The peculiar occurrence of blood residues and lipid-accumulating macrophages in a number of cases led to appellations such as xanthoma, xanthogranuloma, xanthofibroma, etc. Furthermore, mineralized structures can also be found in inflammatory pseudotumors of the lung. In fact, calcifications are even frequent 6, 11, although metaplastic ossification has also been described in at least 10 cases 1,7,9,1O, which brings us to the case at hand. One outstanding characteristic of this case appears to be the considerable extent of ossification. This is at least suggested by the illustrations provided by the authors. However, it is precisely this large mass of newly formed bone which should not lead to a presumptive association with CGCG, since the fibrous and cellular components are usually strongly predominant in CGCG, and the formation of osteoid and new bone is relatively scarce.
Teaching Cases
Giant Cell Granuloma of the
Lung:~
W. W6ckeP, A. Lagemanl, H. Ueberberg2, J. Stumpner3 , H. Suren 4 and H. Mandelkow5 Pathologisches Institut 1, Pneumologische Klinik3, Radiologisches Institut4 und Thoraxchirurgische Abteilung5 des Zentralkrankenhauses Gauting der LVA Oberbayem; Abteilung Experimentelle Pathologie 2, Dr. Karl Thomae GmbH, Biberach an der Riss, FRG
SUMMARY
In a 50-year-old man without bronchopulmonary symptoms a round mass lesion close to the hilum of the right lung was detected in a routine chest x-ray and confirmed by computed tomography. Histological examination of two biopsy specimens did not result in a definitive diagnosis. Therefore thoracotomy with enucleation of the focus was performed. The histological picture of the lesion is characterized by connective tissue proliferation, multinucleated giant cells, ossification, localised hemorrhage, deposits of hemosiderin and foci of foam cells. The findings are interpreted as a giant cell granuloma of the lung.
Introduction Despite knowledge of the clinical status interpretation of histological findings in the bronchial mucosa and transbronchial lung biopsies can be extremely difficult, particularly as only small fragments of tissue material are usually available for examination. We report on tissue alterations not allowing exact diagnosis in the biopsy material. Interpretation of the morphological findings remains problematic in the surgical specimen, especially since we have found only two approximately comparable cases in the literature. Case Report Clinical Data
During a routine examination three weeks prior to admission to our clinic on November 3,1988 a chest x-ray was taken of a male patient born on March 6, 1938. He * Dedicated to Dr. med. habil. V. Haenselt, Bad Berka, on the occasion of his 70th birthday. © 1992 by Gustav Fischer Verlag, Stuttgart
complained of pain in the right shoulder and flush symptoms present for many years. A right suprahilar circular nodule measuring almost 2 em in diameter, projecting into the anterior segment of the upper lobe, was observed. The patient was admitted to hospital with a provisional diagnosis of bronchial carcinoma. On admission the patient gave no history of productive or non-productive cough, shortness of breath, loss of weight or night sweats. He had not smoked for 13 years but prior to that he had smoked 40 cigarettes per day. There had been no antecedent illnesses, apart from surgery for a right inguinal hernia and the incision of anal abscesses 30 years previously. Clinical Findings
On admission the patient measuring 1.75 m and weighing 95 kg presented neither cyanosis nor edema, and there were no lymph nodes palpable. Grade II goitre was present. No abnormalities were detected on percussion and' auscultation of the heart and lungs, B.P. was l40/105 mmlHg and pulse rate 96 beats per min. No abnormality was found on abdominal palpation. A herniotomy scar was present in the right inguinal regIOn. 0344-0338/92/0188-1083 $3.50/0
1084 . W. Wackel et al.
Laboratory Values
Serum uric acid was 7.5 mgldl and gamma GT was 30 Uli. Values for all other routine laboratory tests were normal. Urinary excretion of calcium and serum parathyroid hormone were normal. Two microscopic and cultural investigations of bronchial secretions for tubercle bacilli were negative. The tuberculin test was positive with 10 TU. Radiological Findings
Chest x-rays showed a localised polycyclic density close to the hilum of the right lung, presumably lying in the anterior segment of the upper lobe. Computed tomography (Fig. 1) revealed a homogeneous and calcified round focus (120 HE) measuring 1.7 cm in diameter.
Surgical Findings
A hard, well defined nodule with an irregular surface was palpable close to the hilum in the anterior segment of the right upper lobe. Complete removal was possible. Other intrathoracic findings were normal, in particular no enlarged lympq nodes were detected. The postoperative course was uneventful. Morphological Findings
Biopsies of the bronchial mucosa (E 4260/88 and 4305/88) and surgical specimens (E 4506/88) were stained: Hematoxylin and Eosin, Elastica van Gieson, Berlin blue. The lesion consists of a proliferation of connective tissue containing a variable number of cellular elements. The majority are spindle cells in interlacing rows arranged in a disorderly fashion. Collagen fibres are scattered between the cells. In cellular areas the nuclei appear somewhat polymorphous. Some nucleoli are enlarged and numerous multinuclear giant cells were present behveen the proliferating fibroblast-like cells (Fig. 2). There were many irreg-
Fig. 1. Computed tomography: homogeneous and calcified round focus (H & E, 120) 1.7 em in diameter.
Further Investigations
No abnormalities were found in lung function tests, ECG at rest and under exercise with submaximal effort to 60 W, bone scintigraphy and upper abdominal sonography. Rigid bronchoscopy was performed under general anesthesia and muscle relaxation. There were no abnormalities of the epiglottis and vocal cords. The mucous membrane of the normally patent trachea, the carina and the bronchial system of both lungs were normal. All segmental ostia were normal and patent. The anterior segmental bronchus of the right upper lobe divided into three subsegmental bronchi. In the middle subsegmental bronchus there was a round yellowish mass lesion with a smooth surface and hard consistency. Biopsies were taken from this lesion and the adjoining mucous membrane. As no definitive histological diagnosis could be made, righi-sided anterolateral thoracotomy via the sixth intercostal space was performed.
Fig. 2. Particularly cellular area with numerous multinuclear giant cells (H & E, x 25).
Giant Cell Granuloma of the Lung· 1085
Fig. 3. Many irregular spicules of newly formed bone or osteoid tissue, a few of them in contact with the cartilage of the bronchus (Elastica van Gieson, x 10).
Fig. 4. Bone partly surrounded by osteoblasts (H & E, x 50).
ular trabeculae of newly formed bone or osteoid tissue (Fig. 3), partly surrounded by osteoblasts (Fig. 4). Some trabeculae were immediately adjacent to the cartilage of the bronchial wall. In addition ·focal hemorrhage and siderotic deposits were present in several areas. Occasionally there were small groups of foam cells. Around lacunae caused by the dissolution of cholesterol crystals, foreign body giant cells were present and in one area closely arranged, dilated thin-walled blood vessels were seen (Fig. 6).
exact diagnosis thoracotomy with enucleation of the focus was performed. The histological picture of the excised lesion was characterized by a proliferation of connective tissue, multinucleated giant cells and ossification corresponding to the calcification in the computed tomogram; localized hemorrhage, deposits of hemosiderin and foci of foam cells. The exact interpretation of this process was not possible from the biopsy material alone and even now remains problematic as only two approximately similar cases have been reported in the literature 2, 6. One case described two fused osteoclastoma-like giant cell tumors in the upper lobe of the left lung in a forty-year-old man. Histological confirmation of the diagnosis was obtained by lobectomy. The important difference in the described tumor was the lack of ossification. Interpretation of the findings in the other case report was difficult as it was published in Polish6 . There was no doubt that there was a proliferation of multinuclear giant cells, ossification and focal calcification. The histological findings in our case were most likely compatible with a giant cell granuloma
Discussion In this 50-year-old patient without bronchopulmonary symptoms a round mass lesion close to the hilum of the right lung was detected in a chest x-ray taken during a routine examination. The focus was confirmed by computed tomography and shown to be calcified. There was no indication of the nature of the nodule. As the histological investigation of two biopsy specimens did not result in
1086 . W. Woekel et al.
Fig.S. Aggregates of so-called foam cells (H & E, x 50).
Fig. 6. Area of closely arranged dilated thin-walled blood vessels (H & E, x 25) .
which until recently was known to occur mainly in the mandible 4 and other cranial bones l . The differential diagnosis included a giant cell tumor (osteoclastoma), as it presents in other regions of the skeletons. Only recently it has been reported that apart from the osseous system "giant cell tumors" also occur in the larynx 3 . Eight such cases are to be found in the AFIPOTR-material. The ages of these patients ranged from the second to the seventh decades and males and females were equally affected. Metastases were absent in all of these cases. Occasionally laryngectomy was necessary due to the size of the tumor causing airway obstruction. The histological picture corresponded in some cases to a true giant cell tumor of bone and in other cases to a giant cell granuloma of the facial bones. Because of the prominent vascular pattern in the histological findings in two cases, these were similar to those of an aneurysmal bone cyst. The histological findings in our case therefore correspond to those observed in the larynx. HirschI and Katz I have defined several criteria for differential diagnosis --between giant cell granuloma and giant cell tumor (osteoclastoma). The arrangement of giant
cells in groups around localised hemorrhage, a stroma of oval and spindle-shaped cells with collagen fibres, recent and old hemorrhage with siderotic deposits, small giant cells with numerous irregular nuclei as well as small cells with few nuclei and the formation of osteoid and bone are typical of giant cell granuloma. The giant cell tumor (osteoclastoma) is characterized by a homogeneous distribution of giant cells, a stroma !=omposed predominantly of plump, round or oval cells, slight to moderate hemorrhage with small amounts of hemosiderin, larger giant cells with more nuclei and no ossification. If these differential diagnostic criteria are applied to our case, without taking the completely different organ manifestation into consideration, the findings described in our case are more likely to be those of a giant cell granuloma of the !ung and corresponding with the findings described by Sliwiitska and Iwanik 6 than those of the infrequently occurring pulmonary giant cell tumor mentioned 2 . The fact that an area resembles an aneurysmal bone cyst, as also mentioned by Hyams et aJ.3 is not inconsistent with these findings. The histogenesis of the changes under discussion cannot be answered precisely. Just as in the larynx 3 ossified
Giant Cell Granuloma of the Lung· Letter to the Case· 1087
cartilage as well as connective tissue can be considered as originating in the lungs or the bronchial system. However, further observations are necessary to elucidate this hypothesis. The etiology of this proliferative process is completely obscure. In our opinion it is a reactive rather than a neoplastic process - analogous to the central (reparative) giant cell granuloma of the jaw bone4 . Therefore in contrast to Sliwinska and Iwanik 6 we do not refer to it as a giant cell tumor but prefer to use the term giant cell granuloma.
References 1 HirschI S, Katz A (1974) Giant cell reparative granuloma outside the jaw bone. Diagnostic criteria and review of the
literature with the first case described in the temporal bone. Human Pathol5: 171-181 2 Hofmann D, Jander R, Filler D (1980) Osteoclastoma-like giant cell tumor of the lung. Thorac cardiovasc Surg 28: 444-445 3 Hyams VJ, Batsakis JG, Michaels L (1988) Tumors of the Upper Respiratory Tract and Ear. Atlas of Tumor Pathology. Second Series, Fascicle 25. Armed Forces Institute of Pathology, Washington, D.C. 4 Pindborg Kramer IRH, Torloni H (1971) Histological Typing of Odontogenic Tumours, Jaw Cysts, and Allied Lesions. International Histological Classification of Tumours. No 5. World Health Organization, Geneva 5 Schajowicz F, Ackerman LV, Sis sons HA, Sobin LH, Torloni H (1972) Histological Typing of Bone Tumours. International Histological Classification of Tumours. No 6. World Health Organization, Geneva 6 Sliwinska I, Iwanik J (1975) Guz olbrzymiokomorkowy pluca. Patal pol 26: 535-540
n,
Received October 10, 1989 . Accepted September 19, 1991
Key words: Lung - Giant cell granuloma - Giant cell tumour Prof. Dr. W. Wackel, Pathologisches Institut des Zentralkrankenhauses der LVA Obb., Unterbrunner StralSe 85, D-8035 Gauting, FRG
Letters to the Case D. Dienemann and C.-.A. Hartmann Berlin, FRG
It is true that the lesion described by the authors has a histological similarity with central (reparative) giant cell granuloma of the jawbone (CGCG). However, the histological profile illustrated in this case is not pathognomonic for a particular disease entity, and therefore requires further interpretation according to type and localization of the disease. Thus the histology of brown tumors associ'ated with hyperparathyroidism is nearly identical to that of CGCG, despite a completely different etiology. Since Jaffe traced the origin of CGCG to trauma with progressive hemorrhaging in 1953, which has been demonstrated in a number of instances 4 , CGCG has been interpreted as a reparative product. In the lung there are also morphologically similar transformations which are known under a variety of different names, often called "post-inflammatory tumors" or "inflammatory pseudotumors" 2,3,9,12,13. The cause of these lesions is suspected to be a past case of pneumonia, especially including virus-associated interstitial pneumonia, and the pseudotumor is interpreted as an organiza-
tional product of chronic pneumonia. Several studies 9, 11, 13 have emphasized the heterogeneity of inflammatory pseudotumors, which by no means always have the histological profile of a plasma cell granuloma 1,8, but can have a histiocytoma-like character. The peculiar occurrence of blood residues and lipid-accumulating macrophages in a number of cases led to appellations such as xanthoma, xanthogranuloma, xanthofibroma, etc. Furthermore, mineralized structures can also be found in inflammatory pseudotumors of the lung. In fact, calcifications are even frequent 6, 11, although metaplastic ossification has also been described in at least 10 cases 1,7,9,1O, which brings us to the case at hand. One outstanding characteristic of this case appears to be the considerable extent of ossification. This is at least suggested by the illustrations provided by the authors. However, it is precisely this large mass of newly formed bone which should not lead to a presumptive association with CGCG, since the fibrous and cellular components are usually strongly predominant in CGCG, and the formation of osteoid and new bone is relatively scarce.
