From Metabolic Crisis to Molecular Classification: Multidisciplinary Management of Synchronous Endometrioid Ovarian and Endometrial Carcinomas With Massive Tumor Burden

Background Synchronous endometrial and ovarian carcinomas are uncommon, and distinguishing independent primaries from metastatic disease is essential because staging, prognosis, and adjuvant treatment recommendations differ substantially. Large gynecologic tumor burden usually produces progressive abdominal or pelvic symptoms, but in rare cases the first clinically urgent manifestation may be systemic decompensation. Case Presentation A 53‐year‐old postmenopausal woman with no routine medical or gynecologic care for more than 20 years presented with progressive abdominal distension and constipation. Initial evaluation revealed a 17.7 × 16.1 × 21.2 cm left adnexal mass, a 9.1 × 10.3 × 8.5 cm uterine/myometrial mass, markedly thickened endometrium measuring up to 4.7 cm, large‐volume ascites, pleural effusion, severe hyponatremia, hyperkalemia, and acute kidney injury requiring intensive care admission. Tumor markers were markedly elevated, including CA‐125 of 11,000, CA 19‐9 of 277, and carcinoembryonic antigen of 17.3. Multidisciplinary preoperative stabilization was required before definitive surgical management. The patient underwent total abdominal hysterectomy, bilateral salpingo‐oophorectomy, omentectomy, pelvic lymph node dissection, and lysis of adhesions. Final pathology demonstrated synchronous primary endometrioid carcinomas: a 26.0 cm FIGO grade 2 left ovarian endometrioid adenocarcinoma with microscopic omental involvement, staged as FIGO IIIA2, and a FIGO grade 2 endometrioid endometrial adenocarcinoma with superficial myometrial invasion staged as FIGO 2023 IA2/AJCC pT1a pN0 cM0. Pathology favored synchronous primaries based on superficial uterine invasion, absence of lymphovascular invasion, unilateral ovarian involvement, negative right adnexa, associated endometriosis, and intradepartmental review. Somatic testing showed intact mismatch repair, p53 wild‐type expression, HER2 negativity, microsatellite stability, low tumor mutational burden, and homologous recombination deficiency negativity. Adjuvant carboplatin/paclitaxel was recommended, but the patient declined systemic therapy and proceeded with close surveillance. Conclusion This case highlights that advanced gynecologic malignancy may first declare itself as a metabolic and organ‐compression crisis rather than a classic gynecologic complaint. Safe management required recognition of tumor‐burden–driven physiology, multidisciplinary preoperative stabilization, definitive surgical staging, and integrated morphologic–molecular classification to distinguish synchronous primaries from metastatic disease.