C-KIT mutation in thymic carcinomas.

Abstract

Thymic epithelial tumours are rare malignancies of the anterior superior mediastinum. Several studies have analysed the presence of c-KIT mutations in thymic carcinoma. Immunohistochemical c-KIT expression and mutations in exons 8, 9, 11, 13, 14, 17, and 18 of the KIT gene and in the promoter region of the TERT gene (chr5, 1,295,228C>T/A and 1,295,250C>T) were analysed by PCR based direct sequencing using representative formalin-fixed paraffin-embedded tumour samples of 18 thymic carcinomas. Of 18 patients, 4 test samples were excluded from the study due to inadequate DNA quality. Of 14 patients with thymic carcinomas, KIT and TERT mutation was not detected in any samples. C-KIT expression was associated with nearly a worse overall survival (median time 24.160-49.840, log-rank, p = 0.05). We showed that squamous cell carcinomas led to worse survival than other subtypes. As expected, TNM stage II was significantly correlated with better OS (p = 0.015). Thymic carcinoma is characterised by a KIT-positive and CD5-positive staining pattern. We report a worse overall survival for patients with c-KIT expressing tumours. These data suggest a negative prognostic role for c-KIT expression especially within the first 5 years.