This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
A 69-year-old woman presents with left flank pain and hematuria. Physical examination suggests a left-sided abdominal mass. Computerized tomography (CT) scan of the abdomen reveals a 5-cm mass in the left kidney. Which of the following laboratory abnormalities might also be present? 
Select and explain. 
A. polycythemia, B. thrombocytopenia, C. hypocalcemia, D. leukocytosis
A: polycythemia
Answer: A: polycythemia 
Explanation: (a) Source: (Kasper, pp. 541-542)This patient likely has hypernephroma (renal cell carcinoma). Polycythemia is caused by the production of erythropoietin-like factors. There is no relationship to hypertension. The tumor frequently presents as metastatic disease.