CD44

Formalin-fixed, paraffin embedded tissue block or cell block, or 1 unstained charged slide for each test requested plus 3-4 additional unstained slides cut at 4 microns. Adequate space on each slide for control tissue is required.

CD44 is mainly used, in conjunction with Cytokeratin 20 (CK20) and p53, for the differential diagnoses of urothelial carcinoma in situ (CIS) from reactive urothelial hyperplasia. Urothelial CIS usually demonstrates complete loss of CD44 expression, while reactive urothelial hyperplasia frequently shows strong near full thickness reactivity. The general rule is: for urothelial CIS: CK20+ / P53+ / CD44-, and for reactive: CK20- / P53 - / CD44+ (note: CK20 is positive in umbrella cells and there is wild type staining pattern for p53 in benign urothelium).