Establishing a Cohort of Transgender Men and Gender Nonconforming Individuals to Understand the Molecular Impact of Testosterone on Breast Physiology.

To characterize a cohort of transgender men and masculine-centered gender nonconforming individuals who underwent gender-affirming chest-contouring surgeries at our institution between 2013 and 2018. Demographics, medical history, and breast histopathological assessment for 340 patients were retrieved from medical records. Most of our patients were white, non-Hispanic (75.0%), were taking testosterone (83.2%), and opted for chest-contouring surgery after 12-14 months of testosterone therapy. Ten patients were parous (2.9%). Seventy-nine (23.2%) and 27 (7.9%) patients had a family history of breast cancer or ovarian cancer, respectively. One transgender man was incidentally diagnosed with ductal carcinoma at chest-contouring surgery. Future studies on this cohort will provide valuable insights about the impact of testosterone on breast physiology.