Upper Urinary Tract Urothelial Carcinoma With Squamous, Glandular, and Sarcomatoid Variants in a Horseshoe Kidney: A Novel Case Report and Literature Review.

Horseshoe kidney is a congenital anomaly, which consists of fusion of the lower poles of the kidneys. Cancer in a horseshoe kidney is common, possibly because of the increased risk of chronic obstruction, renal calculi, and recurrent urinary infection. We report a case of a 64-year-old male with a horseshoe kidney who presented to our hospital with gross hematuria and flank pain, which was highly suggestive of pyelonephritis. Comprehensive workup and imaging were performed and showed an extremely rare form of tumor consisting of three histological variants: squamous, glandular, and sarcomatoid. To the best of our knowledge, this is the first case reported with these three histological variants in a horseshoe kidney.