p16 expression in urothelial carcinoma: Experience from a tertiary care center in coastal South India.

Background: Urothelial carcinomas (UC) account for 6 and 2% of all cancers in men and women, respectively. Human papillomavirus (HPV) is one of the causative agents in cancers of the uterine cervix and head and neck. The role of HPV is also being studied in cancers of the urinary bladder, penis, and prostate. As p16-INK4a is a surrogate marker for high-risk HPVE7 oncoprotein, this study aims to highlight the utility of p16 immunohistochemistry (IHC) in the evaluation of HPV-associated UC.
Materials and Methods: A retrospective study was conducted on UC of the bladder received in the Pathology department between January 2013 and December 2018. Bladder biopsies from non-neoplastic lesions served as controls. IHC was done for the detection of the p16 antigen. The p16 staining was recorded as positive, when there was strong staining in >50% of tumor nuclei. The p16 positive and negative tumors were compared based on age, gender, tumor size, grade, and muscle invasion. P value <0.05 was considered statistically significant.
Results: The expression of p16 was analyzed in 72 UC and compared with 20 non-neoplastic cases, of which 26.4% of the cases showed p16 expression. The p16 expression was absent in the non-neoplastic lesions. While the majority (87.5%) of the low-grade tumors were negative for p16 expression, 43.8% high-grade tumors were positive. Similarly, a larger proportion of invasive carcinomas (38.8%) expressed p16 as compared to non-invasive carcinomas (13.8%). Thus, p16 expression showed a significant association with grade and stage in these malignancies (P < 0.05).
Conclusion: The p16 expression was associated with high-grade and muscle-invasive UC. The p16 was absent in all non-neoplastic and precursor lesions. Thus, it can provide essential information not only about HPV association but also on the prognostic implications for the patients.