The significance of carbonic anhydrase (CA-IX) expression in endocervical glandular lesions was determined to assess the utility of CA-IX immunohistochemistry for the identification of gastric-type endocervical adenocarcinoma and its related lesions. In this study, lobular endocervical glandular hyperplasia (LEGH) (n = 5), atypical LEGH (ALEGH) (n = 6), and endocervical adenocarcinomas, including usual-type (UEA) (n = 6) and gastric-type (GAS) (n = 7), were examined by immunohistochemistry for CA-IX expression. The proportion of positive staining and intensity was evaluated as between 0 and 3+. All 13 UEAs and GASs were positive for CA-IX, with 9 cases showing 3+ staining, and 8 cases showing positive areas exceeding 50%. All 11 LEGHs were positive for CA-IX, with all cases showing 50% or more positive areas, although only one case was 3+ positive. Five of 6 ALEGHs were positive for CA-IX, with 4 cases showing 3+ positivity in 100% of the lesion. Non-neoplastic glands were negative for CA-IX, although reserve cell populations and tubal metaplasias were positive for CA-IX. Although CA-IX appears to be involved in tumor progression and may be diagnostically useful in cases of endocervical adenocarcinoma and its precursors, LEGH can be a pitfall, and staining results should be combined with morphology. (C) 2013 Elsevier GmbH. All rights reserved.