Paraneoplastic Hypereosinophilia in Locally Advanced Clear Cell Renal Carcinoma

Renal cell carcinoma (RCC) can cause various paraneoplastic syndromes, including metabolic and hematologic disturbances. Paraneoplastic hypereosinophilia has been reported in a variety of hematologic and solid tumors. Hypereosinophilia due to RCC is very rare and is only available as case reports in the literature. A 66-year-old male patient's thoracoabdominal computed tomography (CT) performed showed an increase in size in the right kidney and a heterogeneous contrasting solid mass of approximately 12 cm × 9 cm, which formed lobulations in its contours. The patient was diagnosed with clear-cell renal carcinoma as a result of a kidney biopsy. In the patient with stage cT4NxM0, the leukocyte count was 40.000/µl and the eosinophil count was 20% in biochemical tests. With these results, the patient was evaluated as having severe paraneoplastic hypereosinophilia due to RCC. The patient was started on sunitinib 50 mg for two weeks on/one week off. No symptoms were observed due to hypereosinophilia. In the evaluation made two weeks after the start of the treatment, it was observed that eosinophil levels decreased to normal rates. Paraneoplastic hypereosinophilia due to renal cell carcinoma may indicate poor prognosis and rapid disease progression. Myelosuppressive therapy is required for symptomatic patients.