Neuroendocrine Tumors in Horseshoe Kidneys: A Review of the Literature With Report of a Novel Finding Expanding Their Morphologic Spectrum.

Horseshoe kidney is a rare congenital anomaly with an unusually higher frequency of neuroendocrine tumors. Symptoms are rare, and, in most of the cases, are incidentally diagnosed. The clinical behavior of these tumors is heterogeneous and can be difficult to predict based on histology alone.