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. The prognosis is very poor, with a 5-year survival rate of <10%. This case highlights the importance of awareness of a very rare and aggressive carcinoma in a patient with long-standing nephrolithiasis.