Document Type

Conference Proceeding

Publication Date

5-1-2026

Abstract

Introduction Thymomas are rare epithelial tumors of the anterior mediastinum, accounting for < 1% of adult malignancies, with an estimated annual incidence of approximately 0.15 cases per 100,000 persons. Although often indolent, thymomas are malignant by definition and may invade locally, recur, and, less commonly, disseminate. They are classically associated with autoimmune conditions, most notably myasthenia gravis, yet their relationship with hereditary cancer syndromes remains poorly defined. Germline BRCA2 mutations are well established in the pathogenesis of breast, ovarian, pancreatic, prostate, and other malignancies through impaired homologous recombination DNA repair. However, an association between BRCA2 mutations and thymic epithelial tumors has rarely been reported. We describe an unusual case of invasive malignant thymoma with pericardial invasion in a BRCA2 mutation carrier, discovered concurrently with a synchronous FDG-avid breast mass suspicious for malignancy. Case Presentation An 85-year-old man with a history of CAD, hypertension, GERD, and prior radical prostatectomy presented with several months of unintentional weight loss and chronic diarrhea. During evaluation for recurrent appendicitis, imaging incidentally revealed a large anterior mediastinal mass measuring up to 7.9 cm with irregular margins. FDG-PET demonstrated moderate metabolic activity within the mass (SUVmax 3.8). CT-guided biopsy revealed a thymic epithelial neoplasm consistent with thymoma. There was no clinical evidence of myasthenia gravis. He subsequently underwent partial sternotomy with thymectomy. Pathology demonstrated a 6-cm type B2 thymoma with direct pericardial invasion, positive surgical margins (R1), and no regional lymph node involvement (pN0), consistent with pT2 stage III disease by the Masaoka–Koga system. Given high-risk features, adjuvant radiation therapy was initiated, with planned surveillance using PET imaging and circulating tumor DNA monitoring. Concurrent PET imaging identified a palpable FDG-avid right breast mass. Genetic testing revealed a pathogenic germline BRCA2 mutation. The breast lesion is currently undergoing diagnostic biopsy and surgical evaluation. Discussion Thymomas are malignant neoplasms with a predilection for local invasion. Type B2 thymomas carry a higher risk of recurrence, particularly in the presence of pericardial invasion or incomplete resection. Complete surgical excision remains the cornerstone of management, while postoperative radiotherapy is recommended in invasive or R1 disease to reduce locoregional recurrence. The coexistence of invasive thymoma and a germline BRCA2 mutation is exceedingly rare and raises questions regarding shared oncogenic mechanisms. While thymic epithelial tumors are not classically associated with BRCA mutations, DNA repair defects may contribute to tumorigenesis in rare malignancies. The presence of a synchronous FDG-avid breast mass in a male BRCA2 carrier further underscores the importance of comprehensive oncologic and genetic evaluation and highlights the need for multidisciplinary management in complex hereditary cancer presentations. Conclusion We report a rare case of malignant type B2 thymoma with pericardial invasion in a BRCA2 mutation carrier, identified alongside a synchronous breast mass suspicious for malignancy. This case highlights the potential intersection between thymic epithelial tumors and hereditary cancer syndromes, reinforces the importance of genetic evaluation in patients with multiple malignancies, and underscores the need for long‑term multidisciplinary surveillance. Further investigation is warranted to elucidate any causal relationship between BRCA‑mediated DNA repair dysfunction and thymoma development.

Comments

American College of Physicians Michigan Chapter and Society of Hospital Medicine Michigan Chapter 2026 Resident and Medical Student Day, May 1, 2026, Troy, MI

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