Secondary malignancies and autoimmune diseases in patients with thymoma and thymic carcinoma: experience from a single tertiary center

Background Thymomas and thymic carcinomas [i.e. thymic epithelial tumors (TETs)] are rare primary tumors accounting for 30%-50% of all anterior mediastinal masses. They are associated with autoimmune diseases, with up to one-third of patients developing myasthenia gravis. In addition, TETs are associated with an increased risk of secondary malignancies. This study aimed to assess the incidence of secondary malignancies and autoimmune diseases in TET patients. Patients and methods We conducted a retrospective, single-center cohort study including TET patients between January 1998 and January 2024. Data on demographics, tumor histology, treatment, autoimmune diseases, and secondary malignancies were extracted from medical records. Standardized incidence ratios (SIRs) for secondary malignancies were calculated using the Netherlands Cancer Registry. Multivariable Cox proportional hazards models were used to identify factors associated with secondary malignancy risk. Results The study included 268 patients (median age: 59 years; 132 men). TET patients were 7.19 times more likely to have a secondary malignancy compared with the general population, whether it was diagnosed before, synchronously with, or metachronous after the diagnosis. The SIRs for the following secondary malignancies during the lifetime of the patients were statistically significant: colon or rectum carcinoma (SIR 13.09), melanoma (SIR 12.19), lymphoma (SIR 11.78), lung carcinoma (SIR 6.80), breast cancer (SIR 3.99), and prostate carcinoma (SIR 3.23). Autoimmune diseases occurred in 37.1% of the entire cohort, with myasthenia gravis (14.3%) being the most prevalent. Conclusions TET patients have a significantly increased risk of secondary malignancies. Future studies should explore the mechanisms underlying this association to improve long-term patient outcomes.