P16 immunostaining patterns in microglandular hyperplasia of the cervix and their significance.
ABSTRACT P16 immunostaining is an important adjunct in the differential diagnosis of difficult squamous and glandular intraepithelial lesions of the cervix. However, unexpected staining of epithelium other than the target lesion can pose a problem in the interpretation. This study examined a common entity in the cervix, microglandular hyperplasia (MGH), that is associated with proliferations of both columnar and squamous epithelial cells-and ascertained the frequency of p16 staining, its pattern, and relationship to human papillomavirus. Fifty-seven cases of MGH were analyzed; 25 scored strongly immunopositive (44%). In 18, staining of the superficial columnar epithelium was patchy, involving 10% to 20% of cells on the surface; in 4 cases, 30% to 40% of cells; and in another 3, over 50% of the cells in a given area were strongly positive. Staining involved both nucleus and cytoplasm of columnar cells. P16 positivity did not colocalize with either cyclin E or MIB-1. Adjacent non-MGH-related columnar epithelium scored negative for p16. Of 25 p16-positive columnar epithelia analyzed, all were human papillomavirus -negative. In conclusion, benign columnar epithelium in the setting of MGH can be expected to stain strongly for p16. Practitioners should be aware of this when evaluating diagnostically difficult squamous or glandular epithelial changes occurring in the setting of MGH or when interpreting cytologic preparations stained with p16.