Metastatic B2 Thymoma in a Patient with Myasthenia Gravis Presenting as a Peri-splenic Mass: A Rare Case Report

Background: Thymomas are rare epithelial tumors of the thymus. Extra-thoracic metastasis is exceptional and typically involves the liver, bone, or soft tissues. Peri-splenic recurrence is exceedingly rare. Case presentation: A 42-year-old female previously treated for thymoma and pleural metastases presented six years later with a peri-splenic mass. CT-guided core biopsy and immunohistochemistry (p40, Pan-CK, TdT, CD3) confirmed metastatic B2 thymoma. Conclusion: This case highlights an unusual pattern of abdominal recurrence and underscores the value of immunohistochemistry in differentiating thymoma metastasis from lymphoma.