P16INK4A immunoexpression and HPV in situ hybridization signal patterns -: Potential markers of high-grade cervical intraepithelial neoplasia

Integration of human papillomavirus (HPV) into the cell genome is considered to be an important event in the progression of cervical neoplasia. p16(INK4a), also a useful biomarker of cervical intraepithelial neoplasia (CIN), shows increased immunoexpression with worsening grades of CIN This study examines the correlation between p16(INK4a) immunoexpression, grade of CIN, HPV type, and HPV in situ hybridization diffuse and punctate signal patterns (linked to episomal and integrated viral particles, respectively) in 44 cervical biopsies/LEEP excisions classified as CIN1 and CIN 2/3. In 22 of 25 (88%) CIN I lesions, p16(INK4a) immunoexpression was confined to the lower half of the epithelium, with sporadic to focal staining in I I of 25 cases (44%). In CIN 2/3 lesions, 15 of 17 (88.2%) showed diffuse, two-thirds to full-thickness staining of the epithelium. High-risk HPV types were found in 20 (80%) CIN I lesions and 17 (100%) CIN 2/3 lesions. Punctate signals were detected in only 3 (13.6%) of high-risk HPV-positive CIN I lesions and in 17 of 17 (100%) CIN 2/3 lesions (P < 0.001). p16(INK4a), immunoexpression and the presence of punctate signal on HPV in situ hybridization correlated with the degree of cervical neoplasia (P < 0.001). However, 3 cases of CIN I demonstrating punctate signals did not demonstrate a comparable CIN 2/3 p16(INK4a) staining pattern. Similarly, two CIN I lesions with comparable CIN 2/3 p16(INK4a) staining showed no evidence of viral integration. Both increased p16(INK4a) immunoexpression and punctate signal correlate with CIN 2/3 grade, supporting the use of either, or both, tests to confirm CIN 2/3. Strong p 16(INK4a) immunostaining in CIN I appears independent of HPV punctate signal type.