Immunocytochemical staining of p16ink4a protein as an adjunct test in equivocal liquid‐based cytology

For cervical cancer screening, HPV-DNA test is expensive and is not easily available in all clinical situations. Thus, we investigated the role of p16ink4a immunostaining as another adjunct test to diagnose cervical neoplasia in equivocal liquid based cytology. Eighty-seven patients were randomly selected for this study (3 patients with normal, 84 patients with abnormal including 24 ASCUS, 30 LSIL, and 30 HSIL). We performed p16ink4a immunostaining on ThinPrep® slide and on each case from the corresponding cervical biopsy tissues. High-risk HPV-DNA testing was also performed on all the subjects. We found that the immunoreactivity of p16ink4a is strongly correlated with the grade of cytologic and histologic diagnoses as well as with Hybrid Capture 2. In comparing the p16ink4a immunostaining with the Hybrid Capture 2 for accuracy of the diagnosis of CIN II/III or a higher-grade disease in the case of ASCUS/LSIL on ThinPrep®, no significant differences were observed. Our data implies that p16ink4a immunocytochemical staining in liquid-based cytology specimens might be used as a good adjunct test to predict cervical histology in equivocal ThinPrep® tests. Diagn. Cytopathol. 2008;36:311–316. © 2008 Wiley-Liss, Inc.