Leukocytosis can be present at any time during various malignancies. A 42-year-old male was admitted to our department for surgical management of his metastatic papillary thyroid cancer. Persistent white blood cell (WBC) elevation with left shift led to a thorough investigation. Having excluded other causes, leukocytosis was attributed to thyroid cancer itself. Positive immunostaining for IL-6 and CEA, as well as elevated serum levels, established this connection.