P16 Expression in Squamous Cell Carcinomas of Cervix and Bladder

Context/Objective: p16 is a widely used immunohistochemical marker in gynecologic pathology. Strong and diffuse cytoplasmic and nuclear expression of p16 in squamous cell carcinomas (SCC) of the female genital tract is strongly associated with high-risk human papilloma virus infection and neoplasms of cervical origin. However, p16 can be expressed in other neoplasms and in several normal human tissues. Occasionally, SCCs may involve both uterine cervix and urinary bladder. Accurate identification of the site of origin in such cases has therapeutic and prognostic implications. We investigate the potential value of p16 expression in this distinction. Design: We reviewed 74 SCCs, 38 (51%) from urinary bladder and 36 (49%) from uterine cervix obtained between 2003 and 2008. Of the 38 cases of bladder carcinoma, 21 occurred in females and 17 in males. Immunohistochemical analysis for p16 (DAKO M7247, clone 484, dilution of 1: 50) expression was done in all cases using the labeled streptavidin-biotin method. Result: Strong and diffuse nuclear and cytoplasmic p16 positivity was observed in 45 cases (61%). Of the 38 SCCs of urinary bladder, 14 (37%) expressed p16 (8 males, 6 females). Of the 36 SCCs of uterine cervix, 31 (86%) were positive for p16. Conclusions: (1) The majority of SCCs of uterine cervix express p16. (2) More than a third of urinary bladder SCCs express p16. (3) SCCs of urinary bladder express p16 independent of gender. (4) p16 immunohistochemical expression alone cannot be used to discriminate between SCCs arising from uterine cervix versus urinary bladder.