Chiara Catania,1 Fabio Conforti,1 Gianluca Spitaleri,1 Massimo Barberis,2 Lorenzo Preda,3 Cristina Noberasco,1 Chiara Lazzari,1 Francesca Toffalorio,1 Filippo de Marinis,1 Michela Manzotti,2 Tommaso Martino De Pas11Division of Thoracic Oncology, 2Division of Pathology, 3Division of Radiology, European Institute of Oncology, Milan, ItalyAbstract: We report the case of a man with an advanced nonkeratinizing squamous cell thymic carcinoma harboring c-KIT exon 13 missense mutation K642E. This aberration is rare and has never been described previously in patients with thymic cancers. It has been found in a small number of cases of gastrointestinal stromal tumor and also in several cases of acral and mucosal melanomas. Some of the patients with gastrointestinal stromal tumor or melanoma harboring this rare mutation have had a tumor response when treated with imatinib. In contrast, in our case, the mutation was associated with primary resistance to full doses of imatinib but, at the same time, it was not a cause of resistance to sorafenib.Keywords: sorafenib, imatinib, thymic carcinoma