[Clinicopathological analysis of gonadal differentiation of sex development disorder]

Objective: To investigate pathological features and differential diagnosis in the gonads with disorder of sex development. Methods: Thirty-six cases of clinically diagnosed hermaphroditism with gonadal biopsy in the Department of Pathology, the Seventh Medical Center of People's Liberation Army General Hospital from April 2007 to July 2021, were collected. All biopsy pathological sections were reviewed, and the gonadal cases with abnormal pathological morphology were screened out. The clinical and imaging data and karyotype of these cases were reviewed. Additional immunohistochemical staining was performed and relevant literature was reviewed. Results: Seven cases of ovotesticular disorder of sex development (OTDSD) were identified, which were characterized by the presence of testicular and ovarian differentiation in the same individual. All patients were under 15 years old and presented with abnormal appearance of external genitalia, and the ratio of male to female was 2∶5. Ultrasonography showed testicular structure in all female patients and cryptorchidism in all male patients. The most common karyotype was 46, XX. One case with undifferentiated gonadal tissue (UGT) and one case with streak gonads were screened out. UGT germ cells were neither in seminiferous tubules nor in follicles, but randomly distributed in an ovarial-type interstitial background, sometimes accompanied by immature sex cords. Streak gonads resembled UGT without germ cells. FOXL2 was positive in granulosa cells, but negative in Sertoli cells. SOX9 expression was opposite. OCT4 was weakly positively/negatively expressed in oocytes and positively expressed in the germ nuclei of UGT. Conclusions: Four differentiation patterns need to be identified in the gonadal biopsy: ovarian differentiation, testicular differentiation, undifferentiated gonadal tissue and streak gonad. The positive expression of SOX9 indicates testicular differentiation, while the positive expression of FOXL2 confirms ovarian differentiation, and the expression of both markers in the same tissue indicates ovotestis differentiation. It is very important to identify UGT, because that has a high probability of developing into gonadoblastoma in the future.