Acute pyelonephritis with anaplastic thyroid carcinoma producing granulocyte colony-stimulating factor

Paraneoplastic leukocytosis was defined as elevated white blood cell (WBC) levels caused by cytokines, likely produced by the tumor itself, without evidence of infection or myeloproliferative disease. We report a case of anaplastic thyroid carcinoma with leukocytosis caused by elevated production of granulocyte colony-stimulating factor (G-CSF) by the carcinoma. Initially, acute pyelonephritis (APN) was diagnosed and treatment for APN was ongoing, but the WBC count steadily increased to 68.8×10⁹/L. She was diagnosed with anaplastic thyroid carcinoma on her neck mass, and the serum concentration of G-CSF was found to be markedly increased at 1,010 pg/mL. In spite of supportive care, the patient's condition rapidly deteriorated and the patient died on day 23 of hospital stay.Leukocytosis without definite evidence of infection could be a paraneoplastic manifestation in patients with malignant tumors, and paraneoplastic leukocytosis may be related to poor prognosis.