(673) Seminoma in SRY-Negative 46, XX Testicular Disorder of Sex Development Presenting as Acute Abdomen: An Extremely Rare Case Report

Introduction 46,XX testicular disorder of sex development (DSD) is a rare condition characterized by testicular differentiation in individuals with a 46,XX karyotype, affecting approximately 1:20,000 phenotypic males. While most cases are SRY-positive due to SRY gene translocation, a minority (10-20%) are SRY-negative, with genetic mechanisms often involving SOX9 or other testis-promoting genes. SRY-negative cases commonly present with ambiguous genitalia and primary amenorrhea. Germ cell neoplasms, particularly seminoma, in SRY-negative 46,XX testicular DSD are exceedingly rare, with fewer than five cases reported in the literature. Acute abdomen due to gonadal torsion as a presenting symptom in these patients has not been previously described. Objective We aim to report an extremely rare case of seminoma in SRY-negative 46,XX DSD, which uniquely presented as an acute abdomen due to gonadal torsion in an adult patient. Methods Case Presentation: A 33-year-old phenotypic female presented with sudden-onset acute abdominal pain and a lifelong history of primary amenorrhea. She had no prior medical evaluation and denied any history of diabetes or hypertension. Physical examination revealed ambiguous external genitalia with posterior labioscrotal fusion, clitoromegaly, underdeveloped breasts (Tanner stage 2), male-pattern androgenic alopecia, mustache, and bilaterally nonpalpable gonads. Pelvic MRI revealed a bulky right adnexal mass measuring 6.8×5.0×5.3 cm with features of gonadal torsion. Emergency right gonadectomy was performed. Intraoperatively, the mass demonstrated a clearly visible lateral sulcus, typical for testis, and an attached epididymal structure (7×1.5×1 cm). Results Gross pathology showed a capsulated oval mass, 11×10×5 cm, with soft grayish-white necrotic tissue and hemorrhage. Microscopically, well-defined tumor tissue arranged in sheets, lobules, and cords of large malignant cells with clear cytoplasm and distinct nucleoli were seen, consistent with classic seminoma. Dense lymphocytic infiltrate and extensive coagulative necrosis were present. The attached tubular structure demonstrated epididymal tissue. Importantly, no ovarian tissue or follicles were identified in any section of the specimen. Surgical margins and tunica were free from tumor. Chromosomal analysis of peripheral blood confirmed a 46,XX karyotype. Further molecular studies showed complete absence of SRY and other Y-chromosome sequences. The final diagnosis was SRY-negative 46,XX testicular DSD with seminoma presenting as acute abdomen secondary to gonadal torsion. The patient recovered well after surgery. Tumor markers (AFP, β-HCG, LDH) were normal. Immunohistochemistry for CD117 and PLAP is pending. Hormonal assessment revealed hypogonadotropic hypogonadism. Genetic counseling and further testing for SOX9, SOX3, and NR5A1 are underway. Multidisciplinary follow-up includes endocrinology, oncology, psychology, and genetic services. Contralateral gonadal evaluation is being planned due to future tumor risk. Conclusions This is one of the exceedingly rare cases of seminoma in SRY-negative 46,XX testicular DSD, and the only reported adult case presenting with acute abdomen due to gonadal torsion. The findings highlight the need to consider DSD in adult patients with atypical genitalia and primary amenorrhea, and to pursue detailed karyotype and pathological analysis. Recognition and management of such rare presentations require a multidisciplinary team to optimize outcomes and address oncologic, endocrine, and psychological needs. Disclosure No