Although data on transgender women is limited, breast cancer screening guidelines in this patient population are evolving. Transgender women have a high prevalence of dense breasts, which is an independent risk for breast cancer. Transgender women differ from non-transgender women in the length of exposure to estrogens as well as variable exposure to progestogens. Therefore, it is recommended that screening not begin in transgender women until after a minimum of 5 years of feminizing hormone use, regardless of age. Some providers may choose to discuss the risks and unknowns with patients and delay screening until after up to 10 years of feminizing hormone use, regardless of age. If you are unsure about when to start screening, it is important to discuss this with your provider.
Source: Fenway Guide to Lesbian, Gay, Bisexual, and Transgender Health and Guidelines for the Primary and Gender-Affirming Care of Transgender and Gender Nonbinary People.