Breast cancer in patients with Lynch syndrome: A single institution retrospective analysis.

Abstract

e22549 Background: Lynch syndrome (LS) is associated with an increased risk of several malignancies including gastrointestinal, genitourinary, gynecologic, skin, and brain cancers. However, whether patients with LS have higher risk of developing breast cancer (BC) or not is still controversial and a relevant clinical question. Methods: From the Santa Maria alle Scotte Hospital registry, we retrospectively identified consecutive patients with LS diagnosed by detecting a germline heterozygous pathogenic or likely-pathogenic variant in MLH1, MSH2, MSH6 or PMS2 on molecular genetic testing within April 2016-January 2022. We compared our sample size to Surveillance, Epidemiology, and End Results Program (SEER) of 2017 National Cancer Institute database. Results: Overall, 43 patients with LS were identified. Of those, 11 (25.6%; 95% CI 1.58-26.72%; p < 0.0001) had histologically confirmed BC, 10 (91%) of whom were hormone receptor positive tumors and BC is the only diagnosis of cancer to date. In this 11 patients median age at diagnosis was 54.5 years. 45% of 11 BC LS patients has germinal MSH2 mutation , 45% of 11% are MSH6 mutaded and has a more aggressive breast cancer. Median follow-up was 3 years and 8 months. All patients are still alive and under treatment. Conclusions: Within the limitations of a small sample size and retrospective design, our analysis suggests a significant association between patients with LS and the diagnosis of primary BC. Validation of such findings through prospective clinical studies with larger samples is warranted and would lead to fundamental modifications to LS screening and follow-up international recommendations.