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Ectopic thymoma mimicking diffuse pleural mesothelioma: A case report
Case Studies ECTOPlC THYMOMA MIMICKING DIFFUSE PLEURAL MESOTHELIOMA: A CASE REPORT HIROAKI FUSHIMI, MD, YOSHIRO TANIO, MD, AND K1YOSHIKOTOH, MD
A case of ectopic thymoma of the pleura with a particular growth pattern mimicking diffuse pleural mesothelloma is reported. Diagnostic imaging showed that the pleural tumor encased the entire left lung. The specimen biopsied from the tumor was composed of lymphocytes and epithelial cells, consistent with the mixed type of thymoma. The autopsy found no evidence of a mediastinal tumor. An involuted thymus was found in the parietal pleural tissue
adhered to the apex of the left lung. The thymoma was thought to originate from the ectopic thymic tissue in the parietal pleura, as a lesion independent from the primary mediasfinal thymoma, and spread along the pleura like diffuse mesothelioma. HUM PATHOL 29:409-410. Copyright © 1998 by W.B. Saunders Company Key words: thymoma, ectopic thymus, pleura. Abbreviations: H&E, hematoxylin and eosin.
The occurrence of thymoma outside the mediastinum is a rare event. 1 Ectopic thymomas of the pleura are rare and have been infrequently reported 2,a although mediastinal thymomas may involve the pleura. 4 This report describes a case of primary thymoma of the parietal pleura simulating diffuse mesothelioma. The histogenesis of ectopic thymuses and thymomas is also discussed.
that the tumor occupied the left pleural cavity, which was densely adherent to the ribs and lung, with slight infiltration to the pulmonary parenchyme and the diaphragm (Fig 2A). There were some areas of necrosis. There was no evidence of mediastinal involvement. Microscopic examination of the tumor found epithelial cells arranged in sheets that were admixed with sheets of small
CASE REPORT A 32-year-old woman was admitted to Osaka Prefectural General Hospital on December 4, 1995, after a mass shadow occupying the entire left lung field on chest roentgenography was observed at another hospital. No clinical history or neurological signs could be found. Chest roentgenography, computed tomography, magnetic resonance imaging, and bone sdntigraphy of the whole body showed a mass occupying the entire left pleural cavity without any metastatic foci. The mediastinum was free of the rumor. Diagnostic considerations included diffuse pleural mesothelioma or advanced bronchogenic carcinoma with pleural dissemination. Needle biopsy of the parietal pleura from the left sixth intercostal space was performed. Microscopically, the specimen contained cell nests separated by fibrous stroma (Fig 1A). The cells in the nests were composed of sheets of small lymphocytes and scattered cells of uniform and polygonal shape (Fig 1B). The polygonal cells had pale, eosinophilic cytoplasms and oval nuclei with very fine chromatin and inconspicuous nucleoli. Immunohistochemical studies of these cells showed diffuse positive staining for keratin (Fig 1C) and epithelial membrane antigen. Results to indicate malignancy, such as cytological anaplasia, necrosis, or mitotic figures, were absent. These results were consistent with the mixed type of thymoma, and this thymoma was considered to originate from the left pleura. The patient gradually deteriorated and finally died of respiratory failure on January 22,1996, despite chemotherapy. POSTMORTEM EXAMINATION Macroscopically, the grayish-white colored, firm, and fibrous tumor replaced the entire left visceral and parietal pleura and encased the entire left lung. A cut section showed From the Department of Pathology- and the Department of Internal Medicine, Osaka Prefectural General Hospital, Sumiyoshiku, Osaka,Japan. Address correspondence and reprint requests to Hiroaki Fushimi, MD, Department of Pathology, Osaka Prefectural General Hospital, 3-1-56 Mandai-Higashi, Sumiyoshi-ku, Osaka, 558-8558,Japan. Copyright © 1998 by W.B. Saunders Company
0046-8177/98/2904-001758.00/0
409
FIGURE1. Histological resultsof the biopsied specimen of the pleural tumor (A) The tumor consists of cell nests separated by fibrous stroma (Hematoxylin and eosin [H&E] stain, original magnification x20.) (B) The cell nests are composed of lymphocytes and polygonal epithelial cells. (H&E stain, original magnification x l00.) (C) Immunohistochemical studies show diffuse positive staining for keratin in the polygonal cells. (Avidin-biotin complex, original magnification x l00.)
HUMAN PATHOLOGY
Volume 29, No. 4 (April 1998) (Fig 2C). This thymic tissue gradually shifted to the thymoma, and in the n e i g h b o r i n g t u m o r o u s tissue some Hassall's corpuscles were also observed. T h e anterior m e d i a s t i n u m did n o t contain involuted thyrnic tissue or t u m o r o u s tissue. DISCUSSION
FIGURE 2. Resultsat autopsy, (A) Macroscopic results of the cut section of the pleural tumor. The grayish-white tumor encases the entire left lung. The arrow indicates the ectopic thymus. (B) Microscopic results of the tumor. Reticular patterns of the epithelial cells with perivascular spaces are marked. (C) Microscopic features of the ectoplc thymus, Lymphoid tissue contains calcificated Hassali's corpuscles (arrows). (B and C, H&E stain, original magnification x50.) lymphocytes. These features were similar to those of the biopsied material. In contrast to the biopsied material, however, great amounts of necrotic areas were apparent. Epithelial elements were p r e d o m i n a n t in some areas, and hyalinotic and dense connective tissues were p r o m i n e n t in o t h e r areas. In addition to the nesting and wabecular patterns of the epithelial component, the organoid features of the tumor, such as reticular patterns with perivascular spaces, were marked (Fig 2B). These results were identical to those of malignant thymoma. In parietal pleural tissue a d h e r e d to the apex of the left lung, brown-colored tissue, m e a s u r i n g 12 X 6 × 6 mm, was observed macroscopically. Microscopically, many calcificated Hassall's corpuscles were identified in the l y m p h o i d tissue. This tissue was considered to be the involuted thymic tissue
T h e histogenesis of ectopic t h y m o m a has b e e n the subject of speculation. T h e most c o m m o n theory to account for thymomas in ectopic locations is that of embryological displacement. Ectopic thymomas have b e e n t h o u g h t to originate f r o m a b e r r a n t thymic tissue trapped during the descent of the thymic p r i m o r d i u m into the anterosuperior mediastinum. 5 In this case, however, the ectopic thymic tissue in the left parietal pleura was considered to be a result of excessive descent of the thymic p r i m o r d i u m . Because the ectopic thymus and the t h y m o m a were located close t o g e t h e r and Hassall's corpuscles were shown in the tumor, the t u m o r may have originated f r o m the ectopic thymus and spread along the pleura as in the case of diffuse mesothelioma. Diffuse pleural involvement of the malignant t u m o r could suggest a primary pleural mesothelioma. It may be difficult for clinicians and pathologists to make a definite diagnosis of a pleural minor of this type because of the unusual clinical appearance of the lesion and its unusual location. This case emphasizes the existence of ectopic t h y m o m a simulating diffuse m e s o t h e l i o m a in pleural diseases. Observation of cell nests c o m p o s e d of epithelial cells and small lymphocytes separated by fibrous stroma should always indicate the possibility of ectopic thymoma. REFERENCES 1. RosaiJ, Levine GD: Tumor of the thymus. 2nd series. Washington, DC, Armed Forces Institute of Pathology, 1975, pp 38-43 2. Moran CA, Travis WD, Rosado-de-Christenson M, et al: Thymomas presenting as pleural tumors. Report of eight cases. Am J Surg Pathol 16:138-144, 1992 3. Honma K, Shimada K: Metastasizing ectopic thymoma arising in the right thoracic cavityand mimicking diffuse pleural mesothelioma--An autopsy study of a casewith reviewof literature. Wien KlinWochenschr 98:14-20, 1984 4. Payne CB Jr, Morningstar WA, Chester EH: Thymoma of the pleura masquerading as diffuse mesothelioma. Am Rev Respir Dis 94:441-446, 1966 5. Suster S, RosaiJ: Histology of the normal thymus. Am J Surg Pathol 14:284-303, 1990
ONCOCYTIC LIPOADENOMA OF THE SUBMANDIBULAR GLAND MITSUYOSHI HIROKAWA, MD, PHD, MICHIO SHIMIZU, MD, TOSHIAm MANAGE, MD, JlSgU ITO, MD, AND SHINJI OGAWA, MD
We report a case of oncocytic lipoadenoma of the submandibniar gland, previously unrecognized benign tumor of the salivary gland. The patient was a 66-year-old Japanese woman with a left submandibulax mass, measuring 11 x 7.5 x 5 cm. Microscopically, the mass was completely surrounded by a thin fibrous connective tissue capsule,
From the Department of Pathology, Kawasaki Medical School, Knrashiki, Japan; the Department of Pathology, Kawasaki Hospital, Okayama, Japan; and the Division of Otorhinolaryngology, Ako Central Hospital, Ako, Japan. Address correspondence and reprint requests to Mitsuyoshi Ilirokawa, MD, PhD, Department of Pathology, Kawasaki Medical School, 577 Matsushima, Kurashiki-city, Okayama, 701-01,Japan. Copyright © 1998 by W.B. Saunders Company 0046-8177/98/2904-001858.00/0
410
and was composed of an intimate admixture of mature fat cells and oncocytes. There have been no English reports of such a neoplasm in the salivary gland with the exception of one recent case report of fipoadenoma of the parotid gland without oncocytic features. We propose the diagnostic term "oncocytic lipoadenoma" for this benign tumor. HuM PATHOL 29:410-412. Copyright © 1998 by W.B. Saunders Company Key words: snbmandibular gland, salivary gland, lipoadenoma, adenolipoma, oncocytoma
Neoplasms of the salivary gland often contain b o t h epithelial and myoepithelial components. Some tumors may be associated with mesenchymal components, such as adipose tissue, cartilage, and b o n e seen in p l e o m o r p h i c a d e n o m a ) We
A case of ectopic thymoma of the pleura with a particular growth pattern mimicking diffuse pleural mesothelloma is reported. Diagnostic imaging showed that the pleural tumor encased the entire left lung. The specimen biopsied from the tumor was composed of lymphocytes and epithelial cells, consistent with the mixed type of thymoma. The autopsy found no evidence of a mediastinal tumor. An involuted thymus was found in the parietal pleural tissue
adhered to the apex of the left lung. The thymoma was thought to originate from the ectopic thymic tissue in the parietal pleura, as a lesion independent from the primary mediasfinal thymoma, and spread along the pleura like diffuse mesothelioma. HUM PATHOL 29:409-410. Copyright © 1998 by W.B. Saunders Company Key words: thymoma, ectopic thymus, pleura. Abbreviations: H&E, hematoxylin and eosin.
The occurrence of thymoma outside the mediastinum is a rare event. 1 Ectopic thymomas of the pleura are rare and have been infrequently reported 2,a although mediastinal thymomas may involve the pleura. 4 This report describes a case of primary thymoma of the parietal pleura simulating diffuse mesothelioma. The histogenesis of ectopic thymuses and thymomas is also discussed.
that the tumor occupied the left pleural cavity, which was densely adherent to the ribs and lung, with slight infiltration to the pulmonary parenchyme and the diaphragm (Fig 2A). There were some areas of necrosis. There was no evidence of mediastinal involvement. Microscopic examination of the tumor found epithelial cells arranged in sheets that were admixed with sheets of small
CASE REPORT A 32-year-old woman was admitted to Osaka Prefectural General Hospital on December 4, 1995, after a mass shadow occupying the entire left lung field on chest roentgenography was observed at another hospital. No clinical history or neurological signs could be found. Chest roentgenography, computed tomography, magnetic resonance imaging, and bone sdntigraphy of the whole body showed a mass occupying the entire left pleural cavity without any metastatic foci. The mediastinum was free of the rumor. Diagnostic considerations included diffuse pleural mesothelioma or advanced bronchogenic carcinoma with pleural dissemination. Needle biopsy of the parietal pleura from the left sixth intercostal space was performed. Microscopically, the specimen contained cell nests separated by fibrous stroma (Fig 1A). The cells in the nests were composed of sheets of small lymphocytes and scattered cells of uniform and polygonal shape (Fig 1B). The polygonal cells had pale, eosinophilic cytoplasms and oval nuclei with very fine chromatin and inconspicuous nucleoli. Immunohistochemical studies of these cells showed diffuse positive staining for keratin (Fig 1C) and epithelial membrane antigen. Results to indicate malignancy, such as cytological anaplasia, necrosis, or mitotic figures, were absent. These results were consistent with the mixed type of thymoma, and this thymoma was considered to originate from the left pleura. The patient gradually deteriorated and finally died of respiratory failure on January 22,1996, despite chemotherapy. POSTMORTEM EXAMINATION Macroscopically, the grayish-white colored, firm, and fibrous tumor replaced the entire left visceral and parietal pleura and encased the entire left lung. A cut section showed From the Department of Pathology- and the Department of Internal Medicine, Osaka Prefectural General Hospital, Sumiyoshiku, Osaka,Japan. Address correspondence and reprint requests to Hiroaki Fushimi, MD, Department of Pathology, Osaka Prefectural General Hospital, 3-1-56 Mandai-Higashi, Sumiyoshi-ku, Osaka, 558-8558,Japan. Copyright © 1998 by W.B. Saunders Company
0046-8177/98/2904-001758.00/0
409
FIGURE1. Histological resultsof the biopsied specimen of the pleural tumor (A) The tumor consists of cell nests separated by fibrous stroma (Hematoxylin and eosin [H&E] stain, original magnification x20.) (B) The cell nests are composed of lymphocytes and polygonal epithelial cells. (H&E stain, original magnification x l00.) (C) Immunohistochemical studies show diffuse positive staining for keratin in the polygonal cells. (Avidin-biotin complex, original magnification x l00.)
HUMAN PATHOLOGY
Volume 29, No. 4 (April 1998) (Fig 2C). This thymic tissue gradually shifted to the thymoma, and in the n e i g h b o r i n g t u m o r o u s tissue some Hassall's corpuscles were also observed. T h e anterior m e d i a s t i n u m did n o t contain involuted thyrnic tissue or t u m o r o u s tissue. DISCUSSION
FIGURE 2. Resultsat autopsy, (A) Macroscopic results of the cut section of the pleural tumor. The grayish-white tumor encases the entire left lung. The arrow indicates the ectopic thymus. (B) Microscopic results of the tumor. Reticular patterns of the epithelial cells with perivascular spaces are marked. (C) Microscopic features of the ectoplc thymus, Lymphoid tissue contains calcificated Hassali's corpuscles (arrows). (B and C, H&E stain, original magnification x50.) lymphocytes. These features were similar to those of the biopsied material. In contrast to the biopsied material, however, great amounts of necrotic areas were apparent. Epithelial elements were p r e d o m i n a n t in some areas, and hyalinotic and dense connective tissues were p r o m i n e n t in o t h e r areas. In addition to the nesting and wabecular patterns of the epithelial component, the organoid features of the tumor, such as reticular patterns with perivascular spaces, were marked (Fig 2B). These results were identical to those of malignant thymoma. In parietal pleural tissue a d h e r e d to the apex of the left lung, brown-colored tissue, m e a s u r i n g 12 X 6 × 6 mm, was observed macroscopically. Microscopically, many calcificated Hassall's corpuscles were identified in the l y m p h o i d tissue. This tissue was considered to be the involuted thymic tissue
T h e histogenesis of ectopic t h y m o m a has b e e n the subject of speculation. T h e most c o m m o n theory to account for thymomas in ectopic locations is that of embryological displacement. Ectopic thymomas have b e e n t h o u g h t to originate f r o m a b e r r a n t thymic tissue trapped during the descent of the thymic p r i m o r d i u m into the anterosuperior mediastinum. 5 In this case, however, the ectopic thymic tissue in the left parietal pleura was considered to be a result of excessive descent of the thymic p r i m o r d i u m . Because the ectopic thymus and the t h y m o m a were located close t o g e t h e r and Hassall's corpuscles were shown in the tumor, the t u m o r may have originated f r o m the ectopic thymus and spread along the pleura as in the case of diffuse mesothelioma. Diffuse pleural involvement of the malignant t u m o r could suggest a primary pleural mesothelioma. It may be difficult for clinicians and pathologists to make a definite diagnosis of a pleural minor of this type because of the unusual clinical appearance of the lesion and its unusual location. This case emphasizes the existence of ectopic t h y m o m a simulating diffuse m e s o t h e l i o m a in pleural diseases. Observation of cell nests c o m p o s e d of epithelial cells and small lymphocytes separated by fibrous stroma should always indicate the possibility of ectopic thymoma. REFERENCES 1. RosaiJ, Levine GD: Tumor of the thymus. 2nd series. Washington, DC, Armed Forces Institute of Pathology, 1975, pp 38-43 2. Moran CA, Travis WD, Rosado-de-Christenson M, et al: Thymomas presenting as pleural tumors. Report of eight cases. Am J Surg Pathol 16:138-144, 1992 3. Honma K, Shimada K: Metastasizing ectopic thymoma arising in the right thoracic cavityand mimicking diffuse pleural mesothelioma--An autopsy study of a casewith reviewof literature. Wien KlinWochenschr 98:14-20, 1984 4. Payne CB Jr, Morningstar WA, Chester EH: Thymoma of the pleura masquerading as diffuse mesothelioma. Am Rev Respir Dis 94:441-446, 1966 5. Suster S, RosaiJ: Histology of the normal thymus. Am J Surg Pathol 14:284-303, 1990
ONCOCYTIC LIPOADENOMA OF THE SUBMANDIBULAR GLAND MITSUYOSHI HIROKAWA, MD, PHD, MICHIO SHIMIZU, MD, TOSHIAm MANAGE, MD, JlSgU ITO, MD, AND SHINJI OGAWA, MD
We report a case of oncocytic lipoadenoma of the submandibniar gland, previously unrecognized benign tumor of the salivary gland. The patient was a 66-year-old Japanese woman with a left submandibulax mass, measuring 11 x 7.5 x 5 cm. Microscopically, the mass was completely surrounded by a thin fibrous connective tissue capsule,
From the Department of Pathology, Kawasaki Medical School, Knrashiki, Japan; the Department of Pathology, Kawasaki Hospital, Okayama, Japan; and the Division of Otorhinolaryngology, Ako Central Hospital, Ako, Japan. Address correspondence and reprint requests to Mitsuyoshi Ilirokawa, MD, PhD, Department of Pathology, Kawasaki Medical School, 577 Matsushima, Kurashiki-city, Okayama, 701-01,Japan. Copyright © 1998 by W.B. Saunders Company 0046-8177/98/2904-001858.00/0
410
and was composed of an intimate admixture of mature fat cells and oncocytes. There have been no English reports of such a neoplasm in the salivary gland with the exception of one recent case report of fipoadenoma of the parotid gland without oncocytic features. We propose the diagnostic term "oncocytic lipoadenoma" for this benign tumor. HuM PATHOL 29:410-412. Copyright © 1998 by W.B. Saunders Company Key words: snbmandibular gland, salivary gland, lipoadenoma, adenolipoma, oncocytoma
Neoplasms of the salivary gland often contain b o t h epithelial and myoepithelial components. Some tumors may be associated with mesenchymal components, such as adipose tissue, cartilage, and b o n e seen in p l e o m o r p h i c a d e n o m a ) We