The oncofetal protein IMP3 : a novel biomarker and triage tool for premalignant atypical endometriotic lesions

OBJECTIVE: To determine whether the oncofetal protein IMP3 is detectable in endometriomas with or without histological atypia and whether IMP3 staining can be used as a triage tool to identify foci of atypical endometriosis in doubtful cases. DESIGN: Retrospective study. SETTING: Academic department and referral center for endometriosis. PATIENT(S): A consecutive series of 516 women who underwent excision of 874 endometriomas. INTERVENTION(S): Histological review by three expert pathologists and immunohistochemical staining for IMP3. MAIN OUTCOME MEASURE(S): Test performance of IMP3 immunohistochemistry versus first-round histology. RESULT(S): The prevalence of atypical endometriosis was 1.7% (95% confidence interval [CI], 0.9%-3.3%) based on the number of women and 1.0% (95% CI, 0.5%-1.9%) based on the number of cysts. Three cases of atypical endometriosis were identified at first-round histological examination. Immunohistochemistry detected seven of the eight cases diagnosed as preneoplastic atypia at second-round histology and one case diagnosed as reactive atypia at second-round histology. The sensitivity of first-round histology was 33.3%, compared with 88.9% of IMP3 immunohistochemistry. CONCLUSION(S): Immunohistochemical staining for IMP3 expression is a simple, inexpensive, and sensitive test that can be used in routine clinical practice as a triage tool to discriminate between cytological/structural atypia and confounding benign conditions