First-trimester ovarian dysgerminoma in pregnancy: a case report highlighting the value of expert ultrasound.

BACKGROUND: Malignant germ cell tumors are rare ovarian malignancies, accounting for less than 5% of ovarian cancers. Dysgerminoma is the most common subtype but remains exceptionally rare during pregnancy, with an estimated incidence of 0.2-1 per 100,000 pregnancies, often complicating timely diagnosis and management. CASE REPORT: A 21-year-old primigravida at 12 weeks and 6 days of gestation was referred for expert ultrasound after detection of a pelvic mass. An ultrasound examination performed by an EFSUMB level III examiner demonstrated an 11.79 × 7.3 cm vascularized solid ovarian tumor (color score 3-4) with heterogeneous echogenicity, a lobulated internal architecture, and smooth outer contours, most suggestive of a primary ovarian malignancy, specifically a dysgerminoma. Serum lactate dehydrogenase was 847 U/L (reference range 135-214 U/L), while CA125 was 34.3 U/mL, remaining within the upper limit of normal (reference range 0.0-35.0 U/mL). Pelvic magnetic resonance imaging confirmed a solid ovarian mass suspicious for dysgerminoma or a stromal tumor. At 15 + 6 weeks of gestation, laparoscopic left adnexectomy with lower transverse laparotomy for specimen extraction was performed. Histopathology confirmed stage IIB left ovarian dysgerminoma with lymphovascular and capsular invasion. Chemotherapy was deferred after multidisciplinary evaluation. The patient delivered spontaneously at 40 + 3 weeks, with no evidence of disease progression postpartum. DISCUSSION: The subjective assessment by expert (Level III) ultrasound examiners helps distinguish between benign and malignant ovarian tumors and refine the diagnosis to a specific histological subtype.