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J Thorac Cardiovasc Surg 2007;133:826-827
© 2007 The American Association for Thoracic Surgery

Brief Communication

Triple thymoma with different histologic types

Division of Thoracic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.

Received for publication September 19, 2006; accepted for publication October 23, 2006.

^_* Address for reprints: Kohei Yokoi, MD, Division of Thoracic Surgery, Department of Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. (Email: k-yokoi{at}med.nagoya-u.ac.jp).

Drs Kawaguchi and Yokoi (left to right)

Multiple thymoma is a rare condition, and only a few double thymoma cases have been reported.^1-3 Among these cases, most had the same histologic subtypes, and so there is argument regarding whether those were multicentric lesions or intrathymic metastases. We present here a case of triple thymoma with different histologic types and discuss the origin of multiple thymoma.

Clinical Summary

A 72-year-old man was admitted to our university hospital after screening because three discrete masses in the anterior mediastinum were noted on his chest computed tomographic scans (Figure 1). The patient was symptom free. Results of physical and laboratory examinations, including the serum level of anti–acetylcholine receptor antibodies, were normal. Total thymectomy with removal of the three tumors was performed through a median sternotomy. The largest firm tumor (Tumor A), measuring 40 x 30 x 16 mm and adherent to the mediastinal pleura, was found at the right lower portion of the thymus. Far from it, the second tumor (Tumor B), measuring 17 x 17 x 12 mm was noted in the right upper portion, and the remaining one (Tumor C), measuring 12 x 12 x 8 mm, was detected in the left lobe of the thymus. No additional tumor was disclosed during the operation. The pathologic examinations of the resected specimens revealed that all three tumors were thymomas with histologic types that were different from each other, according to the World Health Organization classification.⁴ Tumor A had invaded the capsule of the thymoma, and the histologic finding of a proliferation of epithelial cells with relatively large and vesicular nuclei with distinct nucleoli among a heavy population of lymphocytes was compatible with type B2 thymoma. Tumor B was encapsulated, and the histologic feature was predominant lymphocytic forms with scattered plump and round to oval epithelial cells (type B1). Tumor C was also encapsulated and comprised rich lymphocytes and spindle-shaped epithelial cells without nuclear atypia (type AB). Moreover, a focus of thymic epithelial cell hyperplasia was observed in the resected thymus. No adjuvant therapy was performed, and the patient has been well without recurrence for 7 months after surgery.

View larger version (42K): [in this window] [in a new window]   Figure 1. Triple anterior mediastinal masses on chest computed tomography. A, Tumor A (arrow); B, tumors B and C (arrows).

Multiple thymoma has seldom been reported because of its rarity. The incidence in large series has been documented at 0% to 2.2%.^5,6 To our knowledge, there have been only 13 reported cases of double thymoma in the literature, and none of triple or greater thymoma.^1-3 Concerning the histologic types, most cases of multiple thymoma have consisted of tumors of the same type,^1,2 with only 2 cases of double thymoma with different histologic types reported.³

It is possible that the genesis of multiple thymoma involves both intrathymic metastasis and multicentric tumors. Nomori and colleagues¹ described a case of double thymoma in which the histologic, morphometric, and immunohistochemical findings suggested the possibility of intrathymic metastasis rather than multicentric thymoma development. No other reports of multiple thymoma, however, have inferred that the origin was through intrathymic metastasis because of the small number of tumors, similar sizes, and noninvasiveness.^2,3 This case was a triple thymoma with three different histologic types, and we suppose that these three tumors originated independently from different areas of the thymus, because the histopathologic types are classified according to the normal differentiation of the major functional and anatomic compartments of the thymus.⁷ Moreover, hyperplasia of thymic epithelial cells was seen in other thymic tissue of the specimen, although it is not known whether those lesions would grow into a thymoma. From these cases, we suspect that the thymus has a potential to develop multicentric thymomas.

Although we performed a total thymectomy in this case, the extent of the excision for thymoma is controversial even when complete resection is accomplished. Nevertheless, we think that a total thymectomy is the best approach to resection for thymoma because there may be multicentric thymomas.

References

1. Nomori H, Kobayashi K, Ishihara T, Suito T, Torikata C. A case of multiple thymoma: the possibility of intra-thymic metastasis. Jpn J Clin Oncol 1990;20:209-211.[Abstract/Free Full Text]
   
2. Nonami Y, Moriki T. Synchronous independent bifocal orthotopic thymomas. A case report. J Cardiovasc Surg (Torino) 2004;45:585-587.[Medline]
   
3. Yoneda S, Matsuzoe D, Kawakami T, Tashiro Y, Shirahama H, Ohkubo K, et al. Synchronous multicentric thymona: report of a case. Surg Today 2004;34:597-599.[Medline]
   
4. Rosai J, Sobin LH. World Health Organization histological classification of tumours. Histological typing of tumours of the thymus. 2nd ed.. Berlin-Heidelberg: Springer-Verlag; 1999.
   
5. Bernatz PE, Harrison EG, Clagett OT. Thymoma: a clinicopathologic study. J Thorac Cardiovasc Surg 1961;42:424-444.[Medline]
   
6. Maggi G, Casadio C, Cavallo A, Cianci R, Molinatti M, Ruffini E. Thymoma: results of 241 operated cases. Ann Thorac Surg 1991;51:152-156.[Abstract/Free Full Text]
   
7. Marino M, Müller-Hermelink HK. Thymoma and thymic carcinoma. Relation of thymoma epithelial cells to the cortical and medullary differentiation of thymus. Virchows Arch A Pathol Anat Histopathol 1985;407:119-149.[Medline]
   

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This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Kohei Yokoi Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kawaguchi, K. Articles by Yokoi, K. Search for Related Content PubMed PubMed Citation Articles by Kawaguchi, K. Articles by Yokoi, K.