Keratinizing desquamative squamous metaplasia of the kidney mimicking transitional cell carcinoma

A 54-year-old patient, who had a remote history of radial nephrotomy for nephrolithiasis, presented with a symptomatic renal mass. The lesion was suspicious for malignancy on excretory urography, retrograde pyelogram, and computed tomography. A nephroureterectomy was performed. The histologic sections showed keratinizing squamous metaplasia.