Small Cell Carcinoma: a Rare Subtype of Thyroid Cancer with Unanticipated Prognosis

The prognosis of small cell thyroid carcinoma (SCTC) in a large cohort has not been well reported in the literature. In this study, we analyzed the mortality of SCTC, in comparison to medullary thyroid cancer (MTC) and anaplastic thyroid cancer (ATC), based on the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute, to determine the prognosis of SCTC. Information regarding patients with a diagnosis of MTC, ATC, or SCTC, between 2004 and 2013, was acquired from the SEER database. Patient survival curves were assessed by Cox proportional hazards regression analyses, Kaplan-Meier analyses, and log-rank tests. In a Kaplan-Meier analysis of the entire cohort of thyroid cancer patients, cancer-specific survival declined sharply for patients with SCTC, but it declined more modestly for patients with MTC. The cancer-specific survival was not significantly different between SCTC and ATC. Unadjusted Cox regression analysis showed that SCTC had a higher cancer-specific mortality than MTC but a similar prognosis as ATC. SCTC showed a higher cancer-specific mortality than MTC and ATC after adjustments for various confounding factors. SCTC was found to have a more highly lethal clinical course than MTC and had a similar death rate to ATC. Therefore, we recommend that aggressive, radical treatment like surgery or radiation should be performed for these patients.