p16(INK4A) is a surrogate biomarker for a subset of human papilloma virus-associated dysplasias of the uterine cervix as determined on the Pap smear.

Recently, p16(INK4A) has been identified as a biomarker for human papilloma virus (HPV)-induced dysplastic lesions of the cervix and it has been suggested that it may be a useful diagnostic aid for these lesions. This study therefore was performed to determine the utility of p16 expression in a series of Papanicolaou (Pap) smears collected in liquid medium and to determine its benefit, if any, over HPV testing. One hundred seven cases, including 23 negative cases, 34 with low-grade squamous intraepithelial lesion (LSIL), 16 with high-grade squamous intraepithelial lesion (HSIL), 29 with atypical squamous cells of uncertain significance (ASC-US), and 5 cases with ASC suspicious for HSIL (ASC-H), were evaluated for both p16 expression and HPV DNA. We observed p16 expression in only 36% of all cases with abnormal cytology (30/84) and in 40% of all cases associated with high-risk HPV. The highest rate of positivity (80%) and the highest levels of expression (more than three to five positive cells/10x field) were seen in HSIL. Similar results were observed with ASC-H cases. This suggests that in equivocal cases, p16 may be used for confirmation of the diagnosis. On the other hand, p16 positivity was noted in only 21% of LSIL and ASC-US cases. This raises the interesting possibility, given that only a minority of LSIL cases progress on to higher-grade lesions, that p16 might be useful for triaging these patients for closer follow-up and/or further evaluation. Additional studies are required for confirmation.