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

Effect of testosterone therapy on breast tissue composition and mammographic breast density in trans masculine individuals

BACKGROUND

The effect of gender-affirming testosterone therapy (TT) on breast cancer risk is unclear. This study investigated the association between TT and breast tissue composition and breast tissue density in trans masculine individuals (TMIs).

METHODS

Of the 444 TMIs who underwent chest-contouring surgeries between 2013 and 2019, breast tissue composition was assessed in 425 TMIs by the pathologists (categories of lobular atrophy and stromal composition) and using our automated deep-learning algorithm (% epithelium, % fibrous stroma, and % fat). Forty-two out of 444 TMIs had mammography prior to surgery and their breast tissue density was read by a radiologist. Mammography digital files, available for 25/42 TMIs, were analyzed using the LIBRA software to obtain percent density, absolute dense area, and absolute non-dense area. Linear regression was used to describe the associations between duration of TT use and breast tissue composition or breast tissue density measures, while adjusting for potential confounders. Analyses stratified by body mass index were also conducted.

RESULTS

Longer duration of TT use was associated with increasing degrees of lobular atrophy (p < 0.001) but not fibrous content (p = 0.82). Every 6 months of TT was associated with decreasing amounts of epithelium (exp(β) = 0.97, 95% CI 0.95,0.98, adj p = 0.005) and fibrous stroma (exp(β) = 0.99, 95% CI 0.98,1.00, adj p = 0.05), but not fat (exp(β) = 1.01, 95%CI 0.98,1.05, adj p = 0.39). The effect of TT on breast epithelium was attenuated in overweight/obese TMIs (exp(β) = 0.98, 95% CI 0.95,1.01, adj p = 0.14). When comparing TT users versus non-users, TT users had 28% less epithelium (exp(β) = 0.72, 95% CI 0.58,0.90, adj p = 0.003). There was no association between TT and radiologist's breast density assessment (p = 0.58) or LIBRA measurements (p > 0.05).

CONCLUSIONS

TT decreases breast epithelium, but this effect is attenuated in overweight/obese TMIs. TT has the potential to affect the breast cancer risk of TMIs. Further studies are warranted to elucidate the effect of TT on breast density and breast cancer risk.

Systematic Review on Gender-Affirming Testosterone Therapy and the Risk of Breast Cancer: A Challenge for Physicians Treating Patients from Transgender and Gender-Diverse Populations

Conflicting evidence exists about the risk of breast cancer in transgender and gender-diverse (TGD) patients treated with testosterone. This review aimed to summarize current knowledge regarding the risk of breast cancer associated with gender-affirming testosterone treatment (GATT). A systematic literature search using the Preferred Reporting Items for Systematic Review and Meta-Analysis checklist was conducted in January 2023 through Ovid, Scopus, and Web of Science databases. English-language, peer-reviewed articles evaluating breast cancer in TGD patients after GATT that met the inclusion criteria were included. This review included 22 articles, with 14 case reports, 4 case series, and 4 retrospective cohort studies. The review identified 26 TGD patients who developed breast cancer post-GATT therapy, with inconclusive evidence on the relationship between testosterone and the risk of breast cancer in TGD patients. This uncertainty in part arises from the mechanisms governing testosterone's effects within breast tissue, with contrasting theories proposing both proliferative and antiproliferative impacts. Considering this ambiguity, it is imperative for healthcare providers to engage in informed discussions with patients prior to initiating hormone therapy to discuss potential adverse effects, including the possibility of breast cancer development in TGD individuals. Patient education and shared decision-making are essential components of responsible care in this context.

Pragmatic guide to the macroscopic evaluation of breast specimens

The pathological assessment of a breast surgical specimen starts with macroscopic evaluation, arguably one of the most critical steps, as only a small percentage of the tissue is examined microscopically. To properly evaluate and select tissue sections from breast specimens, it is essential to correlate radiological findings, prior biopsies, procedures and treatment with the gross findings. Owing to its fatty nature, breast tissue requires special attention for proper fixation to ensure appropriate microscopic evaluation and performance of ancillary studies. In addition, knowledge of the information necessary for patient management will ensure that these data are collected during the macroscopic evaluation, and appropriate sections are taken to obtain the information needed from the microscopic evaluation. Herein, we present a review of the macroscopic evaluation of different breast specimen types, including processing requirements, challenges and recommendations.

Effect of testosterone therapy on breast tissue composition and mammographic breast density in trans masculine individuals

Objective

Determine the association between TT and breast tissue composition and breast tissue density in trans masculine individuals (TMIs).

Design

This is a cross-sectional study.

Setting

TMIs (n=444) underwent chest-contouring surgeries to treat their gender dysphoria between 2013 and 2019 at an urban medical center.

Participants

Of the 444 TMIs, 425 had pathology images analyzed by our deep-learning algorithm to extract breast tissue composition. A subset of 42/444 TMIs had mammography prior to surgery; mammography files were available for 25/42 TMIs and analyzed using a breast density software, LIBRA.

Main Outcomes and Measures

The first outcome was the association of duration of TT and breast tissue composition assessed by pathologists (categories of lobular atrophy and stromal composition) or by our algorithm (% epithelium, % fibrous stroma, and % fat). The second outcome is the association of TT and breast density as assessed by a radiologist (categorical variable) or by LIBRA (percent density, absolute dense area, and absolute non-dense area).

Results

Length of TT was associated with increasing degrees of lobular atrophy ( p <0.001) but not fibrous content ( p =0.821) when assessed by the pathologists. Every six months of TT was associated with decreased amounts of both epithelium (exp(β)=0.97, 95% CI 0.95-0.98, adj p =0.005) and stroma (exp(β)=0.99, 95% CI 0.98-1.00, adj p =0.051), but not fat (exp(β)=1.01, 95%CI 0.98-1.05, p =0.394) in fully adjusted models. There was no association between TT and radiologist's breast density assessment ( p =0.575) or LIBRA measurements ( p >0.05).

Conclusions

TT decreases breast epithelium and fibrous stroma, thus potentially reducing the breast cancer risk of TMIs. Further studies are warranted to elucidate the effect of TT on breast density and breast cancer risk.

Summary Box

Very little is known about the effect of gender-affirming testosterone therapy on cancer risks, such as breast cancer.Epidemiological studies had different conclusions about the association between testosterone and breast cancer in cisgender women (positive association) and trans masculine individuals (inverse association).More laboratory-based research are needed to understand the effect of testosterone on breast cancer risk in the understudied trans masculine population.Our study provides quantitative histological evidence to support prior epidemiological reports that testosterone may reduce breast cancer risk in trans masculine individuals.

Masculinizing hormone therapy effect on breast tissue: Changes in estrogen and androgen receptors in transgender female-to-male mastectomies

PURPOSE

Almost two percent of individuals in the United States identify as gender non-conforming. In the female-to-male (FTM) transgender population, masculinizing hormone therapy with testosterone is commonly prescribed in gender transition. To date, the effects of exogenous androgens on breast tissue and its roles in altering breast cancer risk are poorly understood. This study examines the histopathologic findings in gender affirming mastectomy (GAM) in transgender FTM patients and the effects of exogenous androgens on estrogen receptors (ER) and androgen receptors (AR).

METHODS

A retrospective review of pathology specimens obtained between 2017 and 2020 was performed comparing androgen exposed breast tissue with breast tissue without androgen exposure. Breast specimens were obtained from patients who underwent FTM GAM with recorded exogenous androgen exposure. Control breast specimens were obtained from reduction mammoplasty (RM) procedures in cisgender women which were aged matched to the GAM cohort, as well as postmenopausal women with benign/prophylactic mastectomy procedures; all controls were without androgen exposure. The histopathologic findings were assessed. Immunohistochemistry for AR and ER was performed and the score interpreted by digital image analysis.

RESULTS

Androgen-exposed breast tissue revealed dense fibrotic stroma, lobular atrophy, thickened lobular basement membranes, and gynecomastoid changes. Longer duration of androgen exposure resulted in a more pronounced effect. The incidence of atypia or cancer was lower in GAM than RM cohort. ER and AR expression was highest in transgender male breast tissue with intermediate duration of exogenous androgen exposure.

CONCLUSION

Increased androgen exposure is associated with lobular atrophy and gynecomastoid changes in breast parenchyma. Overall, ER and AR are expressed strongly in lobular epithelium in patients with prolonged androgen exposure. Exogenous testosterone does not appear to increase risk for breast cancer. Additional studies are needed to investigate the mechanism responsible for these changes at a cellular level and its role in cancer development.

Toker Cell Hyperplasia in the Nipple-Areolar Complex of Transmasculine Individuals

We previously reported breast histopathologic features associated with testosterone therapy in transmasculine chest-contouring surgical specimens. During that study, we observed a high frequency of intraepidermal glands in the nipple-areolar complex (NAC) formed by Toker cells. This study reports Toker cell hyperplasia (TCH)-the presence of clusters of Toker cells consisting of at least 3 contiguous cells and/or glands with lumen formation-in the transmasculine population. Increased numbers of singly dispersed Toker cells were not considered TCH. Among the 444 transmasculine individuals, 82 (18.5%) had a portion of their NAC excised and available for evaluation. We also reviewed the NACs from 55 cisgender women who were aged <50 years old and had full mastectomies. The proportion of transmasculine cases with TCH (20/82; 24.4%) was 1.7-fold higher than cisgender women (8/55; 14.5%) but did not achieve significance (P = .20). However, in cases with TCH, the rate of gland formation is 2.4-fold higher in transmasculine cases, achieving borderline significance (18/82 vs 5/55; P = .06). Among transmasculine individuals, TCH was significantly more likely to be present in those with higher body mass index (P = .03). A subset of 5 transmasculine and 5 cisgender cases were stained for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), androgen receptor (AR), cytokeratin 7, and Ki67. All 10 cases were cytokeratin 7+ and Ki67-; 9 out of 10 cases were AR+. Toker cells in transmasculine cases demonstrated variable expression of ER, PR, and HER2. For cisgender cases, Toker cells were consistently ER+, PR-, and HER2-. In conclusion, there is a higher rate of TCH in the transmasculine than cisgender population, particularly among transmasculine individuals with high body mass index and taking testosterone. To our knowledge, this is the first study to demonstrate that Toker cells are AR+. Toker cell features display variable ER, PR, and HER2 immunoreactivity. The clinical significance of TCH in the transmasculine population remains to be elucidated.

Risk and incidence of breast cancer in transgender individuals: a systematic review and meta-analysis

BACKGROUND AND AIMS

The risk of developing breast cancer in transgender individuals [male-to-female (MtF) or female-to-male (FtM)] is still inadequately quantified. We aimed to evaluate the impact of breast cancer in this population.

METHODS

We conducted a systematic literature search and review using the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines through the PUBMED and SCOPUS databases. We identified six cohort studies (for both populations) plus 35 case reports. Incidence and breast cancer risk quantification were the main outcomes considered.

RESULTS

FtM individuals had a higher risk of developing breast cancer in comparison to cisgender men [standardized incidence ratio (SIR) = 63.4; 95% confidence interval (CI), 32.2-124.9] but a lower risk than cisgender women (SIR = 0.42; 95% CI, 0.07-2.41). Similarly, MtF individuals were at higher risk of developing breast cancer in comparison to cisgender men (SIR = 22.5; 95% CI, 5.54-91.8) and at lower risk than cisgender women (SIR = 0.30; 95% CI, 0.22-0.42).

CONCLUSION

In this systematic study and meta-analysis, we identified that FtM and MtF individuals are at substantially higher risk of developing breast cancer in comparison to cisgender men, though at lower risk than cisgender women. These individuals, in the absence of defined guidelines for breast cancer prevention, should periodically undergo breast or chest examinations.

The Impact of Exogenous Testosterone on Breast Cancer Risk in Transmasculine Individuals

BACKGROUND

Exogenous testosterone is vital to gender-affirming therapy for transmasculine individuals. Testosterone may be implicated in breast cancer (BCa) because it can activate androgen and estrogen receptors. To further explore this risk, we performed a systematic review to investigate the impact of exogenous testosterone on BCa risk in transmasculine individuals.

METHODS

We searched PubMed/MEDLINE and Ovid/Embase for clinical and preclinical studies assessing BCa and testosterone therapy and screened 6125 articles independently. We ascertained level of evidence using a modified tool from Cook et al (Chest. 1992;102:305S-311S) and risk of bias using a modified Joanna Briggs Institute's Critical Appraisal Tool.

RESULTS

Seventy-six studies were included. Epidemiological data suggested that BCa incidence was higher in transmasculine individuals compared with cisgender men but lower compared with cisgender women. Histological studies of transmasculine breast tissue samples also demonstrated a low incidence of precancerous lesions. Interestingly, cases demonstrated that BCa occurred at a younger average age in transmasculine individuals and was predominantly hormone receptor positive. The mechanism for BCa in transmasculine individuals may be related to androgen receptor stimulation or conversion to estradiol. Serum studies reported varied estradiol levels associated with exogenous testosterone. Animal and in vitro studies demonstrated that testosterone was growth inhibitory but may induce proliferation at higher doses or with low estradiol levels.

CONCLUSIONS

Plastic surgeons play a critical role in providing gender-affirming care for transmasculine patients. The limited studies available suggest that this patient population has decreased risk for BCa when compared with cisgender women; however, any BCa that does occur may have different clinical presentations and underlying mechanisms compared with cisgender women and men. Overall, the limitations for clinical studies and discrepancies among preclinical studies warrant further investigation.

Invasive Ductal Carcinoma of the Breast in a Transgender Man: A Case Report

There is limited literature about breast cancer in the transgender population. Very little is known about how gender-affirming hormone therapy affects their breast cancer risk. On the other end, for those diagnosed with breast cancer, there are no clinical guidelines to manage their breast cancer, specifically, how to manage their gender-affirming hormone therapy during breast cancer treatment. Here, we report a 52-year-old transman diagnosed with a grade 2 invasive ductal carcinoma (ER+/PR+/HER2-), and ductal carcinoma in situ (DCIS) of intermediate grade. We discussed his risk factors as well as treatment options.

Oncologic Considerations for Safe Gender-Affirming Mastectomy: Preoperative Imaging, Pathologic Evaluation, Counseling, and Long-Term Screening

SUMMARY

There remain significant gaps in the evidence-based care of patients undergoing gender-affirming mastectomy with regard to implications for breast cancer development and screening. The current clinical evidence does not demonstrate an increased risk of breast cancer secondary to testosterone therapy in transgender patients. Gender-affirmation mastectomy techniques vary significantly with regard to the amount of residual breast tissue left behind, which has unknown implications for the incidence of postoperative breast cancer and need for screening. Subcutaneous mastectomy should aim to remove all gross breast parenchyma, although this is limited in certain techniques. Tissue specimens should also be routinely sent for pathologic analysis. Several cases of incidental breast cancer after subcutaneous mastectomy have been described. There is little evidence on the need for or types of postoperative cancer screening. Chest awareness is an important concept for patients that have undergone subcutaneous mastectomies, as clinical examination remains the most common reported method of postmastectomy malignancy detection. In patients with greater known retained breast tissue, such as those with circumareolar or pedicled techniques, consideration may be given to alternative imaging modalities, although the efficacy and cost-utility of these techniques must still be proven. Preoperative patient counseling on the risk of breast cancer after gender-affirming mastectomy in addition to the unknown implications of residual breast tissue and long-term androgen exposure is critical. Patient awareness and education play an important role in shared decision-making, as further research is needed to define standards of medical and oncologic care in this population.

Testosterone therapy and breast histopathological features in transgender individuals

Testosterone therapy (TT) is administered to enhance masculinization in transgender individuals. The long-term effect of exogenous testosterone on breast tissues remains unclear. Our study evaluated the modulation of breast morphology by TT in transgender individuals with special attention to duration of TT. We reviewed 447 breast surgical specimens from gender affirming chest-contouring surgery, and compared histopathological findings including degree of lobular atrophy, and atypical and non-atypical proliferations between subjects who did (n = 367) and did not (n = 79) receive TT. TT for one patient was unknown. TT for >12 months was associated with seven histopathological features. Longer duration of TT was significantly associated with higher degrees of lobular atrophy (p < 0.001). This relationship remained significant after accounting for age at surgery, ethnicity, body mass index, and presurgical oophorectomy (adjusted p < 0.001). Four types of lesions were more likely to be absent in breast tissues exposed to longer durations of TT: cysts (median = 16.2 months; p < 0.01; adjusted p = 0.01), fibroadenoma (median = 14.8 months; p = 0.02; adjusted p = 0.07), pseudoangiomatous stromal hyperplasia (median = 17.0 months; p < 0.001; adjusted p < 0.001), and papillomas (median = 14.7 months; p = 0.04; adjusted p = 0.20). Columnar cell change and mild inflammation were also less likely to occur in subjects receiving TT (p < 0.05), but were not linked to the duration of TT. Atypia and ductal carcinoma in situ were detected in 11 subjects (2.5%) all of whom received TT ranging from 10.1 to 64.1 months. The incidental findings of high-risk lesions and carcinoma as well as the risk of cancer in residual breast tissue after chest-contouring surgery warrant the consideration of culturally sensitive routine breast cancer screening protocols for transgender men and masculine-centered gender nonconforming individuals. Long-term follow-up studies and molecular investigations are needed to understand the breast cancer risk of transgender individuals who receive TT.

Breast malignancy in female-to-male transsexuals: systematic review, case report, and recommendations for screening

BACKGROUND

Female-to-male (FtM) transsexuals may use testosterone therapy for masculinization, which potentially influences the risk of breast cancer development. Guided by our case report, we aimed to investigate the evidence regarding the risk of testosterone therapy on breast malignancy in female-to-male transsexuals and evaluate breast cancer screening in this subgroup.

METHODS

We conducted a systematic literature search according to the PRISMA checklist in June 2020 in PubMed/MEDLINE and Ovid/EMBASE. Reference lists of included articles were screened to find additional articles that met the inclusion criteria. All cohort studies and case reports evaluating breast cancer in FtM transsexuals after testosterone therapy were included.

RESULTS

We found 23 cases of FtM transsexuals who developed breast cancer after testosterone therapy, including our own case. Moreover, we evaluated ten retrospective cohort studies investigating breast malignancy in the transsexual population. The cohort studies showed no elevated risk in FtM transsexuals compared to natal women. Including our own case, nine cases were described in which breast malignancy was incidentally found during routine histological examination after mastectomy. High-level evidence for a correlation between testosterone therapy and breast malignancy is missing.

CONCLUSION

Few cases are described of FtM transsexuals with breast malignancy. However, cases such as these make physicians aware of the possibility of breast cancer in FtM transsexuals. Radiological screening of FtM transsexuals for breast cancer prior to mastectomy and histological screening of the mammalian tissue after mastectomy should be considered; physicians should decide together with every individual FtM transsexual if screening is necessary.