IMMUNOHISTOCHEMISTRY: P16

P16 EXPRESSION PLAYS A MAJOR ROLE IN THE EVALUATION OF CERVICAL SQUAMOUS INTRAEPITHELIAL LESIONS (SIL) & DISTINGUISHING DYSPLASIA FROM BENIGN MIMICS. OVEREXPRESSION IS SEEN IN MOST HIGH RISK HPV ASSOCIATED SQUAMOUS LESIONS WHEREAS ABSENT / FOCAL WEAK EXPRESSION IS SEEN IN NORMAL / INFLAMED / ATROPHIC CERVICAL EPITHELIUM. P16 EXPRESSION HAS ALSO BEEN SEEN IN NON HPV RELATED TUMORS LIKE HIGH GRADE SEROUS CARCINOMA & ATYPICAL UTERINE SMOOTH MUSCLE TUMORS LIKE LEIOMYOSARCOMAS. TESTING OF OROPHARYNYNGEAL SQUAMOUS CELL CARCINOMAS WITH P16 IS ALSO INDICATED WHERE IT SERVES AS AN EXCELLENT SURROGATE MARKER FOR ACTIVE HPV.