Primary Squamous Cell Carcinoma of the Thyroid: A Population-Based Analysis.

Objectives To analyze the epidemiology and describe the prognostic indicators of patients with primary squamous cell carcinoma of the thyroid. Study Design and Setting Retrospective cohort study based on a national database. Methods The US National Cancer Institute's SEER registry (Surveillance, Epidemiology, and End Results) was reviewed for patients with primary squamous cell carcinoma of the thyroid from 1973 to 2012. Study variables included age, sex, race, tumor size, tumor grade, regional and distant metastases, and treatment modality. Survival measures included overall survival (OS) and disease-specific survival (DSS). Results A total of 199 cases of primary squamous cell carcinoma of the thyroid were identified. Mean age at diagnosis was 68.1 years; 58.3% were female; and 79.4% were white. Following diagnosis, 46.3% of patients underwent surgery; 55.7%, radiation therapy; and 45.8%, surgery with radiation therapy. Kaplan-Meier analysis demonstrated OS and DSS of 16% and 21% at 5 years, respectively. Median survival after diagnosis was 9.1 months. Multivariate Cox regression analysis showed that predictors of OS and DSS included age ( P < .001, P < .001, respectively), tumor grade ( P < .001, P = .001), and tumor size ( P < .001, P = .001). Surgical management was a predictor of OS but not DSS. Conclusion Squamous cell carcinoma of the thyroid is a rare malignancy with a very poor prognosis. Surgical resection confers an overall survival benefit. Age, tumor grade, and tumor size are predictors of OS and DSS.