The role of immunohistochemistry in the evaluation of gynecologic pathology: a single institutional experience.

Although morphology is the cornerstone of diagnostic pathology, it may be necessary to apply ancillary techniques, including immunohistochemistry (IHC) to resolve diagnostic problems. To provide some insights into IHC use in gynecologic (gyn) surgical pathology, we reviewed our institutional experience in using IHC during a 1-year period. A total number of 487 markers were ordered on 203 cases (2.4 markers/case). These 203 represented 4.8% of the 4216 gyn cases that were accessioned during the study period. Immunohistochemistry was used in 22 (9.3%) of 236 vulvar, 13 (9.2%) of 142 vaginal, 92 (5.9%) of 1557 cervical, 59 (3.5%) of 1698 uterine, 1 (0.3%) of 311 fallopian tube, and 16 (6.9%) of 232 ovarian specimens. The most common markers were p16 (n = 125), Ki-67 (n = 69), and p53 (n = 59). Immunohistochemistry proved to be a valuable tool in separating benign from dysplastic or malignant categories, or to increase diagnostic certainty in the latter category, in 131 (65%) of the 203 cases where IHC was requested, and 3.1% of all 4216 gyn cases examined. In the other 72 cases, IHC was utilized to histotype carcinomas, to define a site of origin for an established malignancy, or to assess the expression of predictive markers. Among 6 pathologists, years of practice and time spent on gyn service significantly affected IHC use, with less use with more than 10 years of practice and more than 10 weeks/year of service. This study documents IHC use at a tertiary care academic center and contributes data to define benchmarks for expected IHC use.