Squamous Cell Carcinoma of the Renal Pelvis as a Result of Long-Standing Staghorn Calculi.

We report on a 79-year-old woman with staghorn calculi who presented with severe hypercalcemia. She was later found to have humoral hypercalcemia of malignancy caused by a rare tumor, squamous cell carcinoma of the renal pelvis. Chronic irritation, infection and inflammation from staghorn stones cause squamous metaplasia, leading to squamous cell carcinoma of the renal collecting system.