Triple thymoma with different histologic types

Abstract

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 30 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 17 12 mm was noted in the right upper portion, and the remaining one (Tumor C), measuring 12 12 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. 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.