Assessment of the Utility of PAX8 Immunohistochemical Stain in Diagnosing Endocervical Glandular Lesions.

CONTEXT: PAX8, a member of the paired-box family of genes, is expressed in many tumors of Müllerian origin. However, it is unclear whether PAX8 is a useful marker in diagnosing endocervical glandular lesions because of limited data.

OBJECTIVE

To study the expression of PAX8 in endocervical glandular lesions.

DESIGN

We first studied a cohort of 29 cervical cone biopsies, followed by a second cohort of 17 cases of endocervical adenocarcinoma and 20 cases of uterine endometrioid adenocarcinoma.

RESULTS

In the first cohort, we found that PAX8 was expressed in 23 of 23 (100%) benign endocervical glandular epithelium, 15 of 16 (94%) adenocarcinoma in situ, and 21 of 26 (81%) invasive endocervical adenocarcinoma specimens. In the second cohort, endocervical adenocarcinomas were positive for PAX8 in 14 of 17 (82%), strongly and diffusely positive for p16 in 14 of 17 (82%), positive for carcinoembryonic antigen in 12 of 17 (71%), positive for vimentin in 2 of 17 (12%), and positive for estrogen receptor in 7 of 17 cases (41%). Uterine endometrioid cancer was positive for PAX8 in 20 of 20 (100%), weakly and/or patchy positive for p16 in 17 of 20 (85%), positive for carcinoembryonic antigen in 2 of 20 (10%), positive for vimentin in 19 of 20 (95%), and positive for estrogen receptor in 20 of 20 cases (100%).

CONCLUSIONS

PAX8 is expressed in the majority of benign, premalignant, and malignant endocervical glandular lesions. The usefulness of PAX8 in differentiating endocervical from endometrial lesions is limited.