• GTF2I
• next-generation sequencing
• thymic epithelial tumors
• thymoma

Thymic epithelial tumors (TETs) are rare mediastinal neoplasms originating from thymic epithelial cells. They are classified into thymic carcinomas and thymomas which are further subdivided into A, AB, B1, B2, B3 and micronodular histotypes. Thymomas are often associated with autoimmune diseases, with Myasthenia Gravis being the most common. Few data are available regarding the somatic mutations of TETs limiting our understanding of the molecular pathology of these tumors. Thymomas, especially type A and AB histotypes, frequently exhibit the missense mutation L404H of GTF2I. On the contrary, thymic carcinomas frequently present mutations of CDKN2A, TP53 and CDKN2B. To better understand the molecular aberrations driving the growth of TETs, we conducted a literature review and identified a panel of 77 genes frequently mutated in TETs. We designed a custom assay of next generation sequencing using Illumina DNA Prep with Enrichment kit. We sequence tumor DNA and genomic DNA extracted from blood in 69 patients. By comparing tumor and normal DNA we were able to define somatic mutations of TETs. We confirmed GTF2I mutation the most common in thymomas.