p16INK4A is a surrogate biomarker for a subset of human papilloma virus‐associated dysplasias of the uterine cervix as determined on the Pap smear

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Abstract
Recently, p16INK4A 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/10× 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. Diagn. Cytopathol. 2005;32:21–24.