Breast cancer in transgender patients: A systematic review. Part 1: Male to female.

Male-to-Female (MtF) breast cancer events have been reported since 1968 however, MtF patients' risk of breast cancer remain unclear. Following PRISMA guidelines, electronic databases and grey literature were searched April 2018 to identify breast cancer events in MtF transgender persons. Screening and data extraction were independently performed in duplicate by two reviewers. Study quality was assessed using a component-based system. Qualitative analysis was performed on study characteristics, patient demographics, breast cancer characteristics, and breast cancer presentation and management. Eighteen articles met inclusion criteria representing 22 breast cancer events. Median age at breast cancer diagnosis was 51.5 years. The most common breast cancer type was adenocarcinomas (59.1%) and half of the breast cancers were hormone sensitive, with estrogen receptor positive status in 10 of 19 tested and progesterone receptor positive status in 5 of 14 tested. The most common presentation was breast lump (n = 6, 42.9%), two patients had palpable lymph nodes at presentation (14.3%), and six patients eventually developed metastases (42.9%). Seven patients had a recorded positive breast cancer family history and one was BRCA2 positive. Breast cancers were treated with mastectomies (simple, modified radical, and radical), wide local excision, lumpectomy, or were unclear. Four patients received hormone therapy (23.5%), two received radiation (11.8%), and seven received chemotherapy (41.2%). Breast cancer is present in MtF patients and commonly presents at a younger age with a palpable mass. Major gaps in the literature include lack of transgender population data and long term follow-up. This work highlights the need for screening recommendations.