Lymphoepithelioma-like carcinoma of the renal pelvis

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