[798] Cytokeratin 5/6 Distinguishes Reactive Urothelial Atypia from Carcinoma In Situ and Non-Invasive Urothelial Carcinoma.

Allison Edgecombe, Eric C Belanger, Bojana Djordjevic, Bich N Nguyen, Kien T Mai. The Ottawa Hospital and University of Ottawa, ON, Canada

Background: Cytokeratin 5/6 (CK5/6) is commonly used to differentiate epithelial hyperplasia from atypical hyperplasia and ductal carcinoma in situ in breast. The utility of CK5/6 to distinguish reactive urothelial atypia (RA) from urothelial carcinoma in situ (CIS) and the non-invasive component of papillary urothelial carcinoma (PUC) is not known, and is the focus of this study. CK5/6 performance is compared to that of cytokeratin 20 (CK20) and p16, which have been previously reported as useful markers in this differential.
Design: Twenty consecutive surgical specimens of reactive urothelial atypia (RA) with or without papillary hyperplasia, 40 high grade and low grade papillary urothelial carcinomas (PUC) and 20 CIS were submitted for immunostaining with CK5/6, CK20 and p16. The immunostaining pattern was documented as full urothelial thickness, basal cell layer or umbrella cell layer. The intensity/extent of immunoreactivity was recorded as negative, weak/focal (less than 20% of cells) and strong/diffuse (more than 50% of cells).
Results: Diffuse and strong reactivity involving the full thickness of urothelium was observed with CK5/6 in all cases of RA (100%). p16 and CK20 were negative in all the RA cases (no reactivity or reactivity in the umbrella cell layer). CK5/6 reactivity for CIS and high grade PUC was negative (no reactivity or reactivity in the basal cell layer) in all cases. CK20 was strongly positive (full thickness of urothelium) in 85% of CIS cases and 85% of high grade PUC cases. Strong positive staining for p16 was present in 90% of CIS cases and 80% of high grade PUC cases. Low grade PUC displayed variable reactivity for CK5/6, CK20 and p16.
Conclusions: Strong and diffuse CK5/6 reactivity in RA and negative CK5/6 reactivity (no reactivity or reactivity in the basal cell layer) in CIS and non-invasive PUC may be helpful in distinguishing between these two entities, especially in the setting of negative or weak/focal reactivity for CK20 and p16.
Category: Genitourinary (including renal tumors)

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 176, Tuesday Morning


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