Lymphoepithelioma-like carcinoma of the renal pelvis.

We report the first documented case of undifferentiated carcinoma of the renal pelvis with a prominent lymphoid stroma (lymphoepithelioma-like carcinoma [LELC]). LELCs are morphologically identical to nasopharyngeal carcinoma and are rarely seen in the urinary tract, with only isolated cases involving the urinary bladder and ureter. The tumor was composed entirely of large pale staining malignant epithelial cells with ill-defined borders arranged in syncytial sheets separated by mainly reactive lymphocytes, occasional plasma cells and histiocytes. Tumor cells were immunoreactive to cytokeratin and were negative for leukocyte common antigen. Awareness of LELC is important, as it should be distinguished from lymphoma or inflammatory lesions including, xanthogranulomatous pyelonephritis.