Course Map: Epithelial Tumors: Malignant: Urothelial Carcinoma: Variants of Urothelial Carcinoma: Clear Cell Variant

Clear Cell Variant
These tumors consist of papillary and/or infiltrating carcinoma with the expected growth pattern of other urothelial tumors. The only difference is that the cells are optically clear [63]. They are rich in glycogen and, more often than not, one will find occasional cells with droplets of cytoplasmic mucin. This latter feature, plus the absence of a rich vascular bed, should discourage any thoughts about a metastatic renal cell carcinoma. The clear cell adenocarcinoma will be described later, but those tumors are basically tubular in morphology.
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	Figure 1: Urothelial carcinoma, clear cell variant. The cells are essentially "water-clear," but nuclear features and growth pattern (not evident at this magnification) are typical for urothelial carcinoma.
	Figure 2: Same case as Figure 1. This is a PAS stain showing the abundance of glycogen.
	Figure 3: Same case. Here, the PAS stain has been digested with diastase, removing the glycogen and revealing a droplet of red cytoplasmic mucin (arrow), a feature of many urothelial carcinomas.