The use of p16INK4A immunocytochemistry in “Atypical squamous cells which cannot exclude HSIL” compared with “Atypical squamous cells of undetermined significance” in liquid-based cervical smears

Even though p16INK4a (p16) immunocytochemistryhas proven a useful accessory tool verifying the identification of atypical squamous cells of undetermined significance (ASC-US) categorizedsmears, the procedure still has limitations. To date few studies examining the usefulness of p16 immunocytochemistryin atypical squamous cells which cannot exclude HSIL (ASC-H), compared with ASC-US in liquid-based cervical smears. Therefore, we examined the correlation of p16 immunocytochemical staining with follow-up biopsy results on ASC-H categorizedsmears and compared the data with those classified as ASC-US on 105 liquid-based cytologysamples. We found no statistical significancein the p16 expression of ASC-US smears and the presence of squamous intraepithelial lesions(SIL) in follow-up biopsies (p = 0.546). However, p16 expression did significantly correlate with the presence of SIL (p = 0.002) in ASC-H smears. There was a statistically significantrelationship between p16 expression and presence of high grade squamous intraepithelial lesions(HSIL) or more on the follow-up biopsies in both ASC-US (p = 0.012) and ASC-H (p < 0.001) categorizedsmears. In ASC-US categorizedsmears, there was no statistical significancebetween p16 expression and the HR-HPV viral load(p = 0.091). But there was a statistical significancebetween p16 expression and the HR-HPV viral load(p < 0.001) in ASC-H categorizedsmears. Our results indicate that p16 immunostaining is a much better useful marker for HR-HPV infection and detection of SIL in ASC-H categorizedsmears compared to those defined as ASC-US. Diagn. Cytopathol. 2010. © 2009 Wiley-Liss, Inc.