Retrospective study of a 16 year cohort of BRCA1 and BRCA2 carriers presenting for RRSO: Prevalence of invasive and in-situ carcinoma, with follow-up

Objectives. Carriers of BRCA1 and BRCA2 mutations are at increased risk of high grade serous carcinoma and are therefore offered risk-reducing salpingo-oophorectomy (RRSO) by 40–45 years. Most of these carcinomas are believed to arise in the fallopian tube from serous tubal intraepithelial carcinoma (STIC). We conducted a retrospective study on the prevalence of high grade serous carcinoma and STIC in BRCA1/2 carriers presenting for RRSO, and their follow-up. Methods. Consecutive BRCA1/2 carriers presenting for an RRSO at Erasmus MC (2000–2016) were studied. SEE-FIM pathology protocol was followed from 2010 onwards. For the cases with carcinoma and/or STIC, the histology was reviewed and immunohistochemistry (p53 & MIB-1) was performed. Next Generation Targeted Sequencing (NGTS) for TP53 mutation was used to establish clonality in 2 cases. Results. Of the 527 included patients, 68% were BRCA1, 31.6% were BRCA2, and 0.4% carried both mutations. The prevalence of high grade serous carcinoma was 2.3% (12/527); 59% of these were of tubal origin. High grade serous carcinoma was more common in patients operated on after the recommended age (p = 0.03). Isolated STIC was present in 0.8% (4/527). Two BRCA1 carriers with isolated STIC at RRSO developed peritoneal serous carcinoma N7 years later. Identical TP53 mutations in the peritoneal serous carcinoma and the preceding STIC established their clonal origin. Conclusions. High grade serous carcinoma is more common in BRCA1/2 carriers presenting for RRSO after the recommended age, and is more often of tubal origin. Longer follow up of patients with STIC at RRSO should be considered.

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