Erythrocytosis caused by giant chromophobe renal cell carcinoma: a case report indicating a 9-year misdiagnosis of polycythemia vera

BACKGROUND Erythrocytosis, a rare paraneoplastic syndrome, generally occurs in patients with clear cell renal cell carcinoma and has never been reported in patients with chromophobe renal cell carcinoma. CASE PRESENTATION We report a case of a young man suffering from a giant (22-cm) mass on his left kidney. Because of a history of polycythemia vera, the patient had been treated for the condition for 9 years. Radical nephrectomy was successfully performed, and the postoperative pathologic examination confirmed a diagnosis of chromophobe renal cell carcinoma. Unexpectedly, the symptom of erythrocytosis disappeared after the surgery. Further examination and analysis were performed, and we finally attributed his erythrocytosis to chromophobe renal cell carcinoma. CONCLUSIONS Chromophobe renal cell carcinoma could cause erythrocytosis, but the clear-cut mechanism needs further research. Secondary erythrocytosis such as those related with renal tumors should be taken into consideration during the diagnosis of polycythemia vera.