The use of hormonal therapy and gender-affirming surgery in the transgender community has been rising during the last several years. Although it is generally safe, hormonal therapy’s link to testicular cancer remains uncertain.

To review the incidence of testicular cancer in specimens from gender-affirming orchiectomies at our institution and evaluate the tumors for histologic and genetic alterations.

Pathology reports for gender-affirming orchiectomies (January 1, 2018, to August 1, 2023) were reviewed for testicular neoplasms, with additional analysis for chromosome 12 abnormalities. Incidence and chromosome variations were compared with those in the general population.

Among 458 cases during 5.5 years, 5 germ cell neoplasms in 4 patients emerged. Our institution’s annual incidence rate (159 per 100 000) is 26.5 times higher than the National Cancer Institute’s previous report (6.0 per 100 000). Although they were morphologically no different from germ cell neoplasms in the general population, fluorescence in situ hybridization tests showed no i(12p) in 4 of 5 neoplasms (80%) in our cohort.

The cause behind this rise in incidence remains uncertain but may be due to long term pretreatment with hormones or blockers. The lower isochromosome 12p frequency suggests an alternative mechanism driving tumor development, which requires more detailed molecular studies.

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