Breast Cancer Risk Assessment after Gender-Affirming Chest Masculinization Surgery: The Case for Standardized Documentation and Clinical Guidelines

INTRODUCTION Gender-affirming chest masculinization surgery (GACMS), often termed “top surgery,” is designed to masculinize the chest by excising breast tissue, re-draping skin, and repositioning the nipple-areola complex to align physical appearance with gender identity. Although commonly referred to as a “gender-affirming mastectomy,” this term is a misnomer: most GACMS surgeries are subtotal glandular breast reductions rather than true total mastectomies. These operations intentionally preserve variable amounts of breast tissue to maintain natural contour and to avoid chest wall deformity. The surgical approaches to GACMS are displayed in Figure 1 (written informed consent was obtained from these patients for publication of the images and accompanying clinical information).FIGURE 1.: Gender-affirming chest masculinization surgery approaches. Preoperative (top, left) and postoperative (top, right) views of a transgender male patient who underwent double incision without free nipple-areolar grafts approach and liposuction. Preoperative (middle, left) and postoperative (middle, right) views of a transgender male patient who underwent double incision with free nipple-areolar grafts approach and liposuction. Preoperative (bottom, left) and postoperative (bottom, right) views of a transgender male patient who underwent periareolar approach and liposuction. Published with patient permission.This distinction is clinically significant: preserved tissue results in an unknown but nonzero oncologic risk. Current professional society guidelines offer inconsistent recommendations for postoperative screening, ranging from adherence to cisgender female protocols to complete omission of surveillance. This perspective highlights the need for standardized terminology, accurate documentation, and risk-stratified frameworks for breast cancer assessment after GACMS. We integrate emerging data including limitations of current risk models and postoperative imaging challenges, and propose a multidisciplinary approach incorporating preoperative risk evaluation, quantification of residual tissue, and inclusive surveillance strategies. Establishing such frameworks will promote oncologic safety, surgical precision, and equitable care for transgender and gender-diverse individuals. TERMINOLOGY AND RESIDUAL TISSUE Although widely referred to as a “mastectomy,” GACMS differs fundamentally from oncologic and prophylactic mastectomy. Many techniques—such as double-incision or periareolar approaches—intentionally retain breast parenchyma to optimize chest contour. This surgical nuance has critical implications for cancer risk, documentation, and follow-up. Terminology precision is not merely semantic; inaccurate documentation of “mastectomy” may result in inappropriate cessation of screening or insurance coverage gaps. Operative reports should specify the surgical intent (breast reduction versus mastectomy), the rationale for residual tissue preservation, and the estimated excised glandular volume or mass. We recommend consistent use of the term GACMS to reflect the specific surgical intent and residual anatomy rather than the misleading term gender-affirming mastectomy which can lead to confusion and miscommunication among patients, providers, and insurance companies. Understanding this difference is critical for screening guidelines, which are already fragmented and incomplete. CURRENT SCREENING GUIDELINES: FRAGMENTED AND INCOMPLETE Professional societies offer heterogeneous guidance for transgender men (female to male), most of which is extrapolated from cisgender data, creating uncertainty for clinicians and patients [Table 1]. Table 1 - Organization Post-Mastectomy Recommendation Post-Reduction Recommendation Reference American College of Radiology (ACR) No imaging test is appropriate at any age or risk level; diagnostic imaging (US/MRI) for new symptoms only Mammography or DBT per cisgender female guidelines based on age and risk [1] Endocrine Society Annual clinical breast examination of sub- and periareolar area Mammography per ACS guidelines [2] Fenway Health Annual chest examinations Screening per cisgender female guidelines [3] UCSF Transgender Care No evidence-based guidance; symptom-based evaluation only; mammography usually not feasible; ultrasound or MRI for palpable lesions Screening per cisgender female guidelines [4] WPATH SOC-8 No consensus; shared decision-making with individualized counseling Screening per local cisgender female guidelines [5] AAFP No routine screening required; symptoms warrant further workup Screening per cisgender female guidelines [6] ACOG Limited data to support routine clinical exams; confirm mastectomy vs. reduction before ceasing screening; symptom-based evaluation Continue screening per guidelines [7] NCCN Endorses ACR Appropriateness Criteria Endorses ACR Appropriateness Criteria [8] USPSTF No specific guidelines Biennial mammography ages 40–74 for those with intact breast tissue. [9] ACS No specific guidelines No specific guidelines [10] ASBrS No specific guidelines No specific guidelines [11] Abbreviations: ACR, American College of Radiology; ACS, American Cancer Society; ACOG, American College of Obstetricians and Gynecologists; AAFP, American Academy of Family Physicians; ASBrS, American Society of Breast Surgeons; DBT, digital breast tomosynthesis; NCCN, National Comprehensive Cancer Network; UCSF, University of California, San Francisco; USPSTF, United States Preventive Services Task Force; WPATH SOC-8, World Professional Association for Transgender Health Standards of Care, Version 8. Post-mastectomy refers to gender-affirming bilateral mastectomy. Post-reduction refers to reduction mammoplasty or no chest surgery. All surgical approaches leave some residual breast tissue for cosmetic results; the risk of breast cancer in this residual tissue is unknown. When imaging is indicated for symptoms (chest masses, axillary lymph nodes, nipple retraction, skin changes), mammography is usually not feasible due to limited tissue; ultrasound or MRI are preferred alternatives. High-risk patients (genetic predisposition, significant family history, high-risk pathology) may warrant individualized surveillance strategies regardless of surgery type. This fragmentation underscores the necessity for a unified, risk-stratified and inclusive screening framework specifically adapted for GACMS patients. CANCER RISK AND RISK MODELS Breast cancer risk in transgender men depends on multiple factors: genetic predisposition (eg, BRCA1/2 or other pathogenic germline variants), hormone exposure, family history, and residual tissue volume. While long-term testosterone therapy does not appear to substantially elevate breast cancer risk, based on limited observational data, preserved glandular tissue remains susceptible to neoplastic transformation.12 Meta-analyses suggest that transgender men have a lower lifetime risk than cisgender women but higher than cisgender men.13 However, the true incidence post-GACMS is unknown due to limited longitudinal data and inconsistent reporting. Risk assessment should therefore be performed before surgery, guiding both procedural planning and postoperative surveillance. Existing models—Gail (Breast Cancer Risk Assessment Tool or BCRAT) and Tyrer-Cuzick (International Breast Cancer Intervention Study or IBIS)—do not incorporate transgender-specific variables such as hormonal therapy duration or prior surgeries [Table 2]. In a 2024 Annals of Surgical Oncology study, over 50% of patients seeking GACMS had Tyrer-Cuzick scores ≥17 %, underscoring the need for improved, inclusive tools.14 Table 2. - Comparison of Breast Cancer Risk Assessment Models Characteristic Tyrer-Cuzick or IBIS Model Gail Model (Breast Cancer Risk Assessment Tool or BCRAT) Model Characteristics Clinical Guidelines Generally higher discrimination in high-risk populations More limited discrimination; performs best in average-risk populations Clinical Utility Complex and time-intensive(requires detailed family history) Simpler and quicker to use C-Statistics (predictive accuracy) Generally higher in high-risk cohorts Generally lower discrimination compared with Tyrer-Cuzick in high-risk populations Sensitivity and Specificity Tends toward higher sensitivity at common thresholds; specificity varies by population Lower sensitivity, higher specificity Prediction horizon Estimates both invasive and in situ breast cancer (10-year & lifetime risk) Estimates invasive breast cancer only (5-year & lifetime risk); not intended for people with prior breast cancer or those with DCIS/LCIS Validation in Transgender Men Not specifically validated Not specifically validated Personal Characteristics Age Can be used in women