An extremely rare case of thymic carcinoma manifesting as a liver metastasis: a case report and literature review.

Thymic carcinoma is a rare and aggressive malignancy originating from thymic epithelial cells. We report a case of a 59-year-old male who presented with a progressively enlarging abdominal mass. Physical examination revealed a firm epigastric mass and supraclavicular lymphadenopathy. Chest radiography demonstrated right lower lung consolidation with nodules and left lower lobe infiltrates. Laboratory investigations showed elevated levels of CEA, AFP, LDH, CYFRA 21-1, and PSA. Contrast-enhanced abdominal CT revealed multiple heterogeneous hepatic lesions, the largest measuring 8.7 × 7.4 × 10.8 cm, along with an enhancing right adrenal nodule, suggestive of metastatic disease. Liver biopsy demonstrated a malignant small round blue cell tumor. Initial immunohistochemical analysis showed strong CD117 positivity with negative CK7, LCA, desmin, and S100, initially suggestive of gastrointestinal stromal tumor (GIST), for which imatinib therapy was initiated. However, due to disease progression, a cervical lymph node biopsy was performed, revealing poorly differentiated carcinoma with positive staining for p63 and CD117. Re-evaluation of the initial liver biopsy, supplemented by additional immunohistochemical profiling (p63 and p40 positivity), led to a revised diagnosis of thymic carcinoma, squamous cell carcinoma subtype, with hepatic and nodal metastases. This case highlights the diagnostic complexity of thymic carcinoma with atypical metastatic presentation and underscores the critical role of iterative histopathological evaluation and multidisciplinary collaboration in the management of rare malignancies.