Germline mutations predispose a concurrent thymoma and diffuse large B-cell lymphoma.

Although thymoma is a rare malignancy, it is usually accompanied by secondary cancers. Non-Hodgkin's B-cell lymphoma is one of the most common secondary neoplasms observed in patients with thymoma, presenting before, concurrently with, or after the diagnosis. However, the underlying molecular mechanism of concomitant thymoma and lymphoma remains unclear. This study aimed to report a case with concurrent extrathymic, diffuse large B-cell lymphoma (DLBCL), and thymoma. Published studies and the SEER database were queried to summarize the features of patients with these concomitant cancers. Whole-exome sequencing (WES) was performed on tumor specimens and buccal swab mucosa. Six germline mutations and several specific somatic alterations were found on each neoplastic tissue, which may elucidate the potential pathogenesis of concurrent cancers. This study was novel in reporting concurrent extrathymic DLBCL and thymoma by applying WES on matched neoplasm-normal samples to explore the pathogenesis of these distinct neoplasms.