The role of immunohistochemistry in the evaluation of gynecologic pathology part 2: a comparative study between two academic institutes.

Use of specific immunohistochemistry (IHC) marker, singly or in panels, differs and is influenced by practice setting, individual experience beside other factors. This is a part 2 study where we surveyed the application of IHC in gynecologic (gyn) pathology. Our specific aim in this part was to identify what specific stains are preferentially used. A retrospective chart review on all cases accessioned to the gyn pathology specialty sign out service during a 1-year period was performed at two academic pathology departments. Outside referral and consult as well as gyn cytology cases were excluded from the study. The most commonly ordered markers in diagnostic gyn pathology in descending order of frequency were as follows: P16, ki-67, p53, estrogen receptor (ER), progesterone receptor (PR), and CK7. P16 was used mainly in establishing the diagnosis/grading of squamous intraepithelial lesions (SIL) and differentiating serous from endometrioid carcinomas (ECs). P53 was used particularly in the diagnosis of serous carcinomas and establishing the diagnosis of differentiated vulvar intraepithelial neoplasia. Positive p16 was documented in all high-grade SIL, endocervical carcinomas, and serous carcinomas. In contrast, p16 was negative in all benign, low-grade SIL, and ECs. ER and PR were used in panels with p16, p53, vimentin, and carcinoembryonic antigen to assign tumors to specific site, in differentiating EC from serous carcinomas and in establishing the diagnosis of endocervical adenocarcinomas. Immunohistochemistry was used in 4.7% and 8.7% of gyn surgical path cases at two institutions. P16, ki-67, and p53 were the most commonly used markers especially in grading SIL. This study documents the most commonly used IHC biomarkers at two tertiary care academic centers for defining benchmarks for IHC use.