Rare frequency of gene variation and survival analysis in thymic epithelial tumors.

OBJECTIVE

Thymic epithelial tumor (TET) is a rare mediastinal neoplasm and little is known about its genetic variability and prognostic factors. This study investigated the genetic variability and prognostic factors of TET.

PATIENTS AND METHODS

We sequenced 22 cancer-related hotspot genes in TET tissues and matched normal tissues using Ampliseq Ion Torrent next-generation technology. Overall survival was evaluated using Kaplan-Meier methods and compared with log-rank tests.

RESULTS

A histological analysis of 52 patients with a median age of 52 years showed 15 patients (28.8%) with thymic carcinoma, five with type A thymoma (9.6%), eight with type AB (15.4%), six with type B1 (11.5%), nine with type B2 (17.3%), and nine with type B3 thymoma (17.3%). Three gene mutations were identified, including two with mutation and one with mutation. The three patients with mutant genes included two cases of thymoma (one with and the other with mutation) in addition to a case of thymic carcinoma ( mutation). The 5-year survival rates were 77.7% in all patients. The 5-year survival rates were 93.3%, 90.0%, 76.9%, and 22.9% corresponding to Masaoka stages I, II, III, and IV (<0.001). The 5-year survival rates were 100%, 100%, 83.3%, 88.9%, 65.6%, and 60.9% in the histological subtypes of A, AB, B1, B2, and B3 thymomas, and thymic carcinoma, respectively (=0.012).

CONCLUSION

Hotspot gene mutations are rare in TET. and mutations represent candidate driver genes and treatment targets in TET. Masaoka stage and histological subtypes predict the survival of TET.