Endometrial cancer and endometrial changes in transgender men: Insights from Japanese individuals on testosterone

Endometrial changes in Japanese transgender men (TGM) on testosterone use remain elucidated. This study aims to present TGM with endometrial cancer and insights from a literature review of similar cases. Furthermore, we investigated the correlation between endometrial cancer and severe obesity in TGM who underwent gender-affirming surgery.

Between July 2020 and April 2023, two groups were assessed: 2 TGM with endometrial cancer and 43 TGM without cancer who underwent gender-affirming surgery. A literature review for TGM with endometrial cancer was conducted. Clinical data were retrospectively collected, and histopathological evaluation of female genital organs was performed.

Two TGM with endometrial cancer and an additional four similar cases were identified through a literature search. These TGM had severe obesity (body mass index [BMI] ≥30 kg/m²) and long-term testosterone use, indicating a possible link between endometrial cancer and these factors. Subsequently, we investigated the 43 TGM without cancer. We revealed 30% with obesity (BMI ≥25), only three cases of severe obesity (BMI ≥30), and a significant correlation between testosterone use duration and BMI in TGM without cancer. Histological examination revealed focal proliferative endometrium in 51% of cases and polycystic ovarian changes in 77%.

Our observations suggest a potential link between severe obesity, prolonged testosterone use, and endometrial cancer in transgender men. Histological changes in the female genital tract highlighted frequent focal proliferative endometrium, even under testosterone therapy. Further research should focus on larger, multi-institutional studies to confirm these findings and establish endometrial cancer screening for Japanese TGM.