Primary squamous cell carcinoma of the thyroid associated with leukocytosis and hypercalcemia.

Primary squamous cell carcinoma of the thyroid is an extremely rare, aggressive neoplasm with a uniformly poor prognosis. Described herein is a case of a 66-year-old man with primary squamous cell carcinoma of the thyroid associated with hypercalcemia (13 mg/dL [3.24 mmol/L]) and unexplained leukocytosis (28,400/mm3 [28.4 X 10(9)/L]). The histogenesis of squamous cell carcinoma of the thyroid remains controversial. The associated hypercalcemia and leukocytosis most likely represent a form of paraneoplastic syndrome; possible mechanisms will be discussed in the light of recent studies on tumor-derived mediators.