Abstract Introduction: Breast cancer (BC) is the most diagnosed cancer worldwide, predominantly affecting cisgender women, while in cisgender men it represents only 1-2% of cases. For the transgender population, estimated at 0.5-1% of the general population, there is a significant information gap. BC risk is more complex in this population due to gender-affirming hormone therapies and surgeries. In Brazil, data is even more scarce. Within the Brazilian Unified Health System (SUS) database, the absence of structured mechanisms for recording gender identity since records rely solely on sex assigned at birth renders transgender people largely invisible, hindering equitable care and compromising early detection and management. This is the first nationwide study assessing BC care for transgender patients in Brazil using two complementary approaches: a retrospective analysis of 18 years of SUS database data to identify barriers in care and registration, and a nationwide physician survey to gather insights on institutional preparedness, challenges, and perspectives for screening and treating BC in transgender individuals. Methods: Outpatient records from the SUS database (2008-2025) were analyzed, encompassing a cohort of patients identified through cross-referencing gender-affirming procedure registries as a proxy for transgender identity. BC cases were ascertained via diagnostic codes and oncological treatment records. Complementarily, a nationwide anonymous online survey was conducted with medical oncologists, breast surgeons, gynecologists and other physicians involved in the transgender patients journey across diverse Brazilian regions. The survey explored perceptions regarding screening practices, adherence to clinical guidelines, and institutional readiness to deliver equitable oncological care for this population. Results: Analysis of SUS database records (2008-2025) identified 12,648 patients who underwent gender-affirming procedures. Within this cohort, only six cases of breast cancer were recorded (five in trans men and one in trans woman) representing 0.0005% of the cohort. This figure likely reflects underdiagnosis and underreporting rather than a truly low incidence, although it aligns with trends observed internationally. Additionally, the survey with over 240 physicians, spanning public, private, and mixed healthcare services across all five Brazilian regions, exposed critical gaps in transgender oncology care. Over 65% reported not following specific protocols for transgender patients, nearly 50% acknowledged insufficient knowledge, and almost 80% had not received institutional training or guidance. Collectively, these results underscore the pressing need for inclusive clinical guidelines, structured professional training, and robust health information systems to ensure equitable cancer care for transgender populations. Conclusion: This first nationwide analysis of over a decade of SUS records exposes critical gaps in registration and care. The transgender population remains largely invisible in SUS's information systems, compromising early detection and effective management of BC. The lack of documented cases, combined with systemic barriers such as inconsistent sex/gender registration and insufficient professional training, underscores the need for urgent action. These findings reveal a convergence between database analysis and physician perceptions, pointing to the same structural barriers. To address them, it is essential to improve health information systems, implement comprehensive professional training, and establish inclusive public health policies. Citation Format: I. C. Schultz, J. L. da Silva, L. Landeiro, N. C. Nunes, R. Sant’Ana, G. Onzi, N. Viana. Breast Cancer Profile and Healthcare Practices Among Transgender Patients within the Brazilian Unified Health System: a mixed cross-sectional and survey study (TRANSformation) abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-12-21.
Schultz et al. (Tue,) studied this question.