Diagnostic Discordance in a 46,XX Ovarian Dissecting Gonadoblastoma with Dysgerminoma Transformation and Leydig Cell Tumor: Hyperandrogenism, β-hCG Elevation, and CEUS Findings

Background and Clinical Significance: The current WHO classification recognizes gonadoblastoma and mixed germ cell–sex cord-stromal tumor, unclassified, as distinct ovarian germ cell–sex cord-stromal tumors. Their heterogeneous components may generate discordant endocrine, biochemical, and imaging findings. Case Presentation: An 18-year-old nulliparous woman with a 46,XX peripheral blood karyotype presented with progressive virilization and an enlarging left ovarian mass. Preoperative total testosterone was >16,000 pg/mL and β-human chorionic gonadotropin (β-hCG) was 192.0 IU/L. Magnetic resonance imaging (MRI) and transrectal contrast-enhanced ultrasound (CEUS) favored an androgen-producing sex cord-stromal tumor; CEUS showed heterogeneous hyperperfusion with mildly disorganized intratumoral vessels. Computed tomography (CT) suggested a mixed germ cell tumor, and frozen section favored a steroid cell tumor while not excluding a focal germ-cell component. Fertility-sparing surgery was performed. Final pathology showed dissecting gonadoblastoma with dysgerminoma transformation and trophoblastic differentiation, combined with a Leydig cell tumor. Serum β-hCG fell to 80.4 IU/L on postoperative day 1 and to <0.2 IU/L by January 2026, accompanied by androgen normalization and resumption of menstruation. At 6.5 months, the patient remained clinically well; ultrasound showed a normal right ovary and no evident left adnexal mass, although contemporaneous endocrine and tumor-marker measurements were unavailable. Conclusions: In a heterogeneous ovarian tumor, the dominant phenotype may represent only one component. Discordance among endocrine findings, tumor markers, and imaging should prompt consideration of mixed histology. β-hCG elevation in an androgen-secreting ovarian tumor may indicate an occult germ-cell or trophoblastic component, whereas CEUS should be interpreted as a vascular phenotype rather than a histology-specific signature.