Renal cell carcinoma producing granulocyte colony-stimulating factor.

Severe neutrophilia caused by renal cell carcinoma secreting granulocyte colony-stimulating factor (G-CSF) is a rare manifestation of renal cancer. A 70-year-old woman presented with a 2-year history of severe anemia, severe neutrophilia and elevated serum G-CSF, which completely resolved after radical nephrectomy. Histologic study revealed a histologically high-grade, stage pT1N0M0 renal cell carcinoma. Serum G-CSF level was elevated preoperatively and returned to normal postoperatively. Immunohistochemical study of the tumor tissue using anti-G-CSF monoclonal antibody revealed positive staining in the cancer cells. Careful follow-up of white blood cell count and physical examination for neck lymph node enlargement led to the timely identification of tumor recurrence 17 months after surgery, which resulted in prompt and successful salvage immunotherapy. In this case, G-CSF appeared to contribute to the leukocytosis, as both serum G-CSF level and white blood cell count closely correlated with the clinical tumor growth. White blood cell count should be closely monitored as an indicator of disease activity in patients with G-CSF-producing renal cell carcinoma.