Introduction: Gender-affirmation therapy for transgender individuals is an area of increasing importance in genitourinary pathology. These patients undergo various forms of hormonal replacement therapy (HRT) followed by bilateral orchiectomy. To date, there are very limited studies on the histological and biochemical alterations in these testes. Methods: We conducted a retrospective search of the database for gender-affirming orchiectomies performed at our institution from 2018 to 2022. Clinical features, including age, length and types of hormonal treatment, and pathologic features, were reviewed and summarized. 19 cases were subjected to whole slide imaging scanning for digital analysis using the Leica system. Immunohistochemistry for OCT4 and CD117 was performed on selected cases. Results: Atrophic changes and decreased spermatogenesis were found in all the gender-affirming orchiectomy specimens examined, with decreased mean tubule diameter (102.9 µm, 202 tubules examined) compared to the tubular size of germ cell neoplasia in situ (GCNIS) and normal testis (139.3 µm and 143.7 µm, 326 and 185 tubules examined, respectively). All cases showed significant maturation arrest, with 55 testes showing aspermatogenesis and the remaining 14 testes showing hypospermatogenesis. Various degrees of basement membrane thickening were observed in all testes, and 55.1% of the testes were found to have focal tubule hyalinization/obliteration. The number of Leydig cells was reduced, with marked cytoplasmic vacuolization and degenerative changes. In a subset of specimens, scattered germ cells displayed prominent nucleomegaly. Using digital analysis, the average nuclear size of these abnormal germ cells was 14.4 µm in diameter (35 cells counted), approaching or exceeding the size of the neoplastic nucleus in GCNIS (mean diameter=12.1 µm, 33 cells counted). However, the enlarged nuclei of these germ cells demonstrated a smooth nuclear membrane, small nucleoli, and fine granular and smudged chromatin, significantly different from the nuclei in GCNIS. Furthermore, immunohistochemistry staining of the germ cells with nucleomegaly in tested cases demonstrated negative staining for both OCT4 and CD117, militating again the possibility of GCNIS. Conclusions: All the testes from gender-affirming orchiectomies in our study exhibit significantly reduced spermatogenesis, including maturation arrest and atrophic changes. In addition, the presence of scattered germ cells with nucleomegaly in these specimens can mimic GCNIS. SOURCE OF Funding: NA
