Utility of p16(ink4a) immunocytochemistry in liquid-based cytology specimens from women treated for high-grade squamous intraepithelial lesions

OBJECTIVE: To examine whether p16(ink4a) immunocytochemical (ICC) expression detected intraepithelial disease in liquid-based cytology (LBC) specimens from women with high-grade squamous intraepithelial lesions (HSIL), whose specimen was labeled negative for intraepithelial lesion or malignany (NILM). STUDY DESIGN: Residual LBC specimens from women treated for HSIL (n = 21), whose LBC test was interpreted as NILM including marked benign inflammatory changes (BCC) were used. The control (n = 25) consisted of residual LBC specimens from women with documented HSIL. ICC for p16p(16k4a) was performed on a second ThinPrep (ThinPrep 2000, Cylyl Corporation, Boxborough, Massachusetts, U.S.A.) preparation; the percentage ofpositive cells and intensity of immunostaining were recorded. Standard LBC preparations for p16(ink4a) ICC-positive and ICC-negative control cases were reviewed. RESULTS: Twenty-four of 25 (96%) of the HSIL control group were ICC p16(ink4a) positive. In the NILM/BCC group, 2 of 21 with adequate LBC residua were ICC p16(ink4a) positive; on review both were reclassified as epithelial abnormality--1 HSIL and 1 atypical squamous cells cannot exclude HSIL. In both, subsequent colposcopic biopsy yielded HSIL. CONCLUSION: p16(ink4a) ICC positivity on NILM/BCC LBC residua from patients with HSIL may identify cases that merit cytologic review and possible reclassification. The utility of p16(ink4a) ICC in this situation requires further study.