An extremely rare case of thymic squamous cell carcinoma complicated with B3 thymoma and myasthenia gravis: a case report.

Background: Thymomas complicated with myasthenia gravis are conventionally treated during thoracic surgery. Particularly, invasive thymomas are resected alongside the surrounding organs. Here, we present a case where surgical and perioperative management was performed under the presumption of thymoma with myasthenia gravis. However, definitive pathology revealed the co-occurrence of B3 thymoma and thymic squamous cell carcinoma. This case highlights the unique presentation and exceptional rarity of thymomas that are complicated by myasthenia gravis and thymic carcinoma.

Case presentation: A 65-year-old female presented with eyelid ptosis at our hospital. Following a comprehensive examination, the patient was diagnosed with myasthenia gravis. Her computed tomography (CT) scan revealed an anterior mediastinal tumor suggestive of a thymoma, prompting a referral to the Department of Thoracic Surgery. Moreover, preoperative assessment could not definitively exclude pericardial invasion. She subsequently underwent an extended thymectomy via a longitudinal sternal incision. The tumor exhibited partial invasion of the pericardium, necessitating resection and reconstruction. Definitive pathological examination confirmed the co-occurrence of B3 thymoma and thymic squamous cell carcinoma. Positive lymph node metastasis classified the patient as stage IVa according to the Union for International Cancer Control (UICC) TNM Classification of Malignant Tumors, 8th Edition, and she was started on adjuvant radiotherapy postoperatively. Currently, the patient remains under observation, with follow-up CT scans showing no signs of recurrence.

Conclusions: This report describes an extremely rare case of thymoma complicated with myasthenia gravis and thymic squamous cell carcinoma.