Verrucous carcinoma of the renal pelvis: case presentation and review of the literature.

Squamous cell carcinoma (SCC) of the renal pelvis is an uncommon tumour that has occasionally been associated with horseshoe kidney. The verrucous form of well-differentiated SCC has not been described previously at this site. We describe such a tumour in a 41-year-old man, who presented with gross haematuria and recurrent pyelonephritis caused by staghorn calculi within a horseshoe kidney. Histology showed extensive keratinising squamous metaplasia of the pelvic urothelium with an area of verrucous acanthosis and underlying invasion of the pelvic smooth muscle by broad tongues of squamous epithelium without atypia. Local lymph nodes were not involved by tumour. Immunohistochemistry and polymerase chain reaction revealed no evidence of human papillomavirus infection. The literature regarding verrucous carcinoma of the urothelial tract is reviewed.