Immunocytochemical colocalization of P16(INK4a) and Ki-67 predicts CIN2/3 and AIS/adenocarcinoma.

BACKGROUND: Although previous studies have shown that p16(INK4a) and Ki-67 are sensitive and specific markers for high-grade lesions (≥CIN2) on cervical biopsies, limited information is available regarding the performance of a dual-staining approach as a diagnostic adjunct in cervical cytology. We evaluated a dual p16(INK4a)/Ki-67 immunocytochemistry (ICC) assay to determine its sensitivity and specificity versus that of high-risk HPV (HR-HPV) in a US-based pilot cytology study.

METHODS: ThinPrep specimens from 122 cervical cytology specimens encompassing 23 negative (NILM), 20 ASC-US, 22 LSIL, 17 ASCH, 22 HSIL, and 18AGC cases were processed for multiplexed ICC staining using a CINtec Plus Kit. Dual-positive assay results were defined based on the detection of 1 or more epithelial cells that were stained for both p16INK4a and Ki-67 without regard to cellular morphology. HR-HPV testing was performed by multiplex PCR with capillary electrophoresis genotyping.

RESULTS: Dual staining for p16(INK4a) and Ki-67 was frequently detected in HSIL and AGC but was rarely detected in NILM cases. The HR-HPV assay showed a sensitivity of 76.2% and a specificity of 55.8% for the detection of clinically significant cervical squamous or endometrial lesions. In contrast, the colocalization of p16(INK4a) plus Ki-67 maintained a high sensitivity of 81.8% and improved specificity to 81.8% for biopsy-confirmed CIN2/3, endocervical adenocarcinoma, or endometrial adenocarcinoma.

CONCLUSIONS: Dual staining for p16(INK4a)/Ki-67 immunocytochemistry dramatically increased specificity and maintained high-level sensitivity for the diagnosis of CIN2/3 or glandular lesions compared with PCR-based testing for HR-HPV.