Secretory Carcinoma of the Thyroid Gland: Report of a Highly Aggressive Case Clinically Mimicking Undifferentiated Carcinoma and Review of the Literature.

After being described in the salivary glands as a malignancy with features essentially identical to those of the breast, secretory carcinoma (SC) (formerly mammary analogue SC) has now been identified in other sites including the skin, lung, and thyroid gland. In the breast, SC has a relatively favorable prognosis. Likewise when arising in the salivary glands, it is generally considered to be a low to intermediate grade carcinoma; however, there is a range of clinical behavior with occasional patients dying of progressive disease. SCs of the thyroid gland are rare, and reports suggest a relatively aggressive behavior, at least relative to well differentiated carcinomas such as papillary carcinoma and minimally invasive follicular carcinoma. We present a patient with a highly aggressive thyroid gland SC that mimicked undifferentiated carcinoma clinically. The patient had widespread metastatic disease and died rapidly from airway compromise. We also review the literature for reported cases of thyroid gland SC in order to better establish the clinical features and expected clinical course of such tumors occurring at this site.