Mucinous and squamous metaplasia of the renal pelvis.

Mucinous and squamous cell metaplasia of the transitional cell epithelium occurs in response to chronic irritation and is predominantly found in the bladder. When the 2 forms of metaplasia occur simultaneously they usually are associated with malignancy. We report 2 cases of mucinous and squamous metaplasia of the epithelium of the renal pelvis that were not associated with malignancy. This is believed to be the fourth report of this divergent metaplasia. The mechanism for these changes is discussed.