Metastatic Thymic Carcinoma with novel KIT mutations masquerading as a Carcinoma of Unknown Primary Site

A patient diagnosed with thymic carcinoma was found to have three KIT mutations (F522C, V560del, and Y823S), two of them not previously documented. In addition, this is the first reported case of thymic carcinoma with more than one pathogenic KIT mutation. He was initially treated with imatinib mesylate (IM) with a minor response. Subsequently, IM was discontinued, and he was treated with cisplatin plus gemcitabine with clinical and radiologic response. A repeat liquid biopsy showed total suppression of V560del, Y823S, F522C, and KRAS amplification.