Synchronous and metachronous malignancies after malignant struma ovarii in the seer database

BACKGROUND/AIM: Second primary tumors (SPTs) often occur, either synchronous or metachronous. Struma ovarii is a rare ovarian tumor represented by thyroid tissue in the ovary. Among other factors, production of thyroid hormones by the tumor or a shared genetic predisposition can further influence the development of SPTs. The occurrence of SPT, either synchronous or metachronous, following a long follow-up, has never been considered extensively. PATIENTS AND METHODS: We analyzed the Surveillance, Epidemiology, and End Results (SEER) database from 1973 to 2011 to follow-up all the cases of malignant struma ovarii in an effort of calculate the occurrence of SPTs in this cohort of patients. RESULTS: We identified 21 patients with malignant struma ovarii in the period between January 1973 and December 2011. In a follow-up period of 219.57 person-years, 3 patients had SPT. One patient had synchronous thyroid sclerosing carcinoma, 1 patient had metachronous papillary adenocarcinoma with a latent time of 7 years and 1 patient had synchronous salivary ductal carcinoma. CONCLUSION: Up to date, only thyroid synchronous tumors have been reported in the literature. A synchronous and a metachronous thyroid tumor, plus a synchronous salivary gland tumor, were found. A significant association between malignant struma ovarii and thyroid/salivary gland cancer is herein demonstrated.