Variation of Gonadal Dysgenesis and Tumor Risk in Patients With 45,X/46,XY Mosaicism

Abstract OBJECTIVE To describe the gonadal features of patients with 45,X/46,XY mosaicism, and to evaluate the prevalence of gonadal tumor in different phenotypes. MATERIALS AND METHODS The medical records of consecutive patients with 45,X/46,XY karyotype or its variants who had undergone gonadal biopsy or gonadectomy at a single institute between 1996 and 2017 were retrospectively reviewed. RESULTS Of 34 patients with 45,X/46,XY mosaicism, a unilateral dysgenetic testis and a contralateral streak gonad was detected in 20 patients (59%), bilateral streak gonads in nine (26%), and bilateral dysgenetic testes in five (15%). A gonad composed of both streak and dysgenetic testicular portions was observed in seven gonads of six patients. All streak gonads were removed, and bilateral gonadectomy was performed in 15 patients raised as girls. Pathological examination revealed gonadal tumors in six of the 34 (18%) patients, including a gonadoblastoma in seven gonads among five patients and an association of dysgerminoma with gonadoblastoma in one gonad. All six patients who developed gonadal tumor had female genitalia. Postoperative course was uneventful except one boy. A seminoma was developed in his soritaly scrotal testis at the age of 16 years. CONCLUSION The prevalence of gonadal tumor in patients with 45,X/46,XY mosaicism may vary according to the phenotype, and high in patients with female phenotype. Considering the increased risk of gonadal tumors in such patients, early investigation and individual management, including prophylactic gonadectomy, are recommended. In male patients, a close follow-up of the preserved testes is mandatory until adulthood.