Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (557 page)

This very rare rennin-secreting tumor is a benign tumor that mainly affects adolescents and young adults, with peak prevalence in the second and third decades of life.

   Who Should Be Suspected?

The main characteristics of this tumor are hypertension and hyperaldosteronism secondary to excessive rennin secretion by tumor cells. Patients typically present with headache, retinopathy, double vision, dizziness, nausea, polyuria, and proteinuria.

   Laboratory Findings

   Plasma rennin activity (PRA) is increased, with levels significantly higher in the renal vein from the affected side.

   Hyperaldosteronism and hypokalemia.

RENAL CELL CARCINOMA

   Definition

Renal cell carcinoma (RCC) originates from the lining of the proximal tubule. It is the most common type of kidney cancer, responsible for 80–85% of primary renal neoplasms and 2–3% of all malignant diseases in adults.

   Who Should Be Suspected?

   RCC is more common in males than females (2:1 ratio), with a typical presentation in the sixth and seventh decades of life. Many patients are asymptomatic until later stages of the disease. The classic triad of RCC (hematuria, flank pain, and palpable renal mass) occurs in only 9% of patients and usually suggests advanced disease.

   At least four hereditary syndromes associated with renal cell carcinoma have been recognized, including von Hippel-Lindau syndrome, hereditary papillary renal carcinoma, familial renal oncocytoma, and hereditary renal carcinoma.

   Laboratory Findings

   Urinalysis: microscopic or gross hematuria, which can be associated with the presence of clots.

   Complete blood count (CBC) shows anemia, either normal or microcytic; anemia usually precedes the diagnosis of RCC by several months. Erythrocytosis is found in up to 5% of patients due to increased production of erythropoietin.

   Serum testing may show hypercalcemia and increased serum ferritin.