Osteoclast-like giant cell tumor of the renal pelvis associated with urothelial carcinoma: computed tomography, gross, and histologic appearance.

Osteoclastoma-like giant cell tumor of the renal pelvis, similar to the entity more commonly occurring in bone, is very rare, having been reported in twelve previous cases to our knowledge. This is the first report of this entity, to our knowledge, to include its cross-sectional imaging appearance. A hyperdense area within the lesion on non-contrast CT may correspond with extensive hemorrhagic content of the lesion identified histologically. As in most prior cases, an adjacent smaller urothelial carcinoma of the renal pelvis was also identified. In the limited reported cases, this entity has exhibited highly aggressive behavior with poor prognosis.