p16 Immunohistochemistry in Colposcope-Directed and Random Cervical Biopsies of CIN2 and CIN3.

OBJECTIVE

The aim of this study was to determine if there is a different p16 expression pattern between colposcope-directed and random (colposcope-undetectable) biopsies of cervical intraepithelial neoplasia (CIN2) and CIN3.

METHODS

Cervical biopsies that were positive for CIN2 or CIN3 were selected from a database of samples acquired during a large population-based clinical trial in Guangdong Province in China (Shenzhen Cervical Cancer Screening Study II). Blocks were recut, reread, and then immunostained for p16. Biopsies were categorized as either colposcope-directed or random biopsies. Diffuse staining was considered p16 positive, whereas focal or no staining was considered p16 negative. Differences were determined by the Fisher exact test.

RESULTS

Among the patients with CIN3, there were 232 individual biopsies of CIN3. Sixty were randomly collected, and 172 were colposcopy directed. p16 positivity for the colposcope-directed and random biopsies was 97.7% and 91.7%, respectively (p = 0.052). Like the CIN3 biopsies, colposcope-directed and random CIN2 samples expressed p16 similarly (86.8% [46/53] and 82.6% [19/23], p = .73, respectively).

CONCLUSIONS

Based on our data, even small colposcope-undetectable biopsies of CIN3 are significant. Random biopsies of CIN2 or CIN3 demonstrate similar p16 positivity as visible lesions and therefore might be expected to have a similar natural history.