P3.019: Low-Grade Serous Ovarian Carcinoma in an Adolescent: A Case Report

Introduction: Malignant ovarian tumors in adolescent patients are rare, accounting for only 1% of all cancers in patients under 15 years. However, a pelvic mass in pediatric patients has a malignancy rate ranging from 16% to 55%. Low-grade serous carcinoma (LGSC) is an uncommon subtype, comprising less than 10% of serous ovarian carcinomas. Unlike high-grade serous carcinoma, LGSC has a better prognosis but demonstrates resistance to chemotherapy. It may arise de novo or develop from a borderline ovarian tumor. Genetically, KRAS (19–55%), NRAS (25%), and BRAF (5%) mutations are frequently observed, whereas TP53 mutations are uncommon. LGSC predominantly affects adult women, making its occurrence in an adolescent patient exceedingly rare.

Case Description: We report a case of a 15-year-old female who presented to the emergency department in July 2023 with a nine-month history of progressive abdominal pain and vomiting. A computed tomography (CT) scan revealed bilateral ovarian tumors (124 × 72 mm and 57 × 52.3 mm), thick-walled cystic lesions with septations, peritoneal carcinomatosis, and mild ascites (Figure 1). Laboratory workup showed an elevated CA-125 level of 228 U/mL. On July 28, 2023, she underwent exploratory laparotomy, bilateral salpingo-oophorectomy, omentectomy, and appendectomy. Intraoperative findings included right and left ovarian tumors measuring 10 cm and 6 cm, respectively, with peritoneal carcinomatosis and 1000 cc of clear peritoneal fluid. Histopathological examination confirmed LGSC with right ovarian capsule involvement, omental infiltration, and malignant peritoneal fluid (Figure 2). Immunohistochemical analysis revealed wild-type TP53 expression. Postoperatively, the patient completed six cycles of paclitaxel, carboplatin, and bevacizumab until January 2024. A follow-up magnetic resonance imaging (MRI), in February 2024 showed no evidence of active pelvic lesions. The last CA-125 measurement was 10.14 U/mL. The patient is currently on outpatient maintenance therapy with bevacizumab every 21 days.

Discussion: LGSC in adolescents is extremely rare, as it typically affects women in their 40s and 50s. The diagnosis can be challenging due to its rarity and often subtle presentation. CA-125 is a valuable biomarker for prognosis and treatment response monitoring. Various imaging techniques, including ultrasound, CT, MRI, and positron emission tomography (PET), play roles in diagnosis and surveillance. PET imaging is particularly useful for detecting disease recurrence. Although LGSC has a relatively favorable prognosis, over 80% of patients experience disease relapse, necessitating aggressive management. Treatment options include cytoreductive surgery, chemotherapy with bevacizumab, hormonal therapies, targeted therapies, and clinical trial participation. While no standardized treatment protocol exists for recurrent disease, individualized approaches should be considered.

Conclusion: LGSC can present as advanced disease and should be included in the differential diagnosis of ovarian tumors in adolescent patients. Multimodal treatment strategies are essential to improve long-term survival outcomes.