A 52-year-old postmenopausal woman from Delhi presents with progressive abdominal distension and mild abdominal pain for 3 months. On examination, she has ascites and a palpable abdominal mass. Serum CA-125 is markedly elevated at 850 U/mL. Ultrasound shows a large complex ovarian mass with solid and cystic components, and free fluid in the pelvis. CT abdomen reveals omental caking and peritoneal nodules. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis **Key Point:** The combination of postmenopausal status, markedly elevated CA-125 (>800 U/mL), ascites, omental caking, peritoneal nodules, and a complex solid-cystic ovarian mass is pathognomonic for advanced epithelial ovarian cancer, specifically high-grade serous carcinoma (HGSC). ## High-Grade Serous Carcinoma (HGSC) — Defining Features | Feature | HGSC | Benign Cystadenoma | Granulosa Cell Tumor | |---------|------|-------------------|---------------------| | **Age** | Postmenopausal (peak 50–70 yr) | Reproductive age | Postmenopausal (peak 50–60 yr) | | **CA-125** | Markedly elevated (>500 U/mL) | Normal or mildly ↑ | Normal | | **Presentation** | Advanced stage (ascites, peritoneal spread) | Asymptomatic or mass effect | Abnormal bleeding, endometrial hyperplasia | | **Imaging** | Solid, heterogeneous, ascites, omental caking | Simple or multilocular cyst | Solid, homogeneous | | **Prognosis** | Poor (5-yr OS ~40% stage III/IV) | Excellent (>95%) | Intermediate | ## Pathologic Hallmarks of HGSC 1. **Nuclear atypia:** High-grade nuclei with coarse chromatin, prominent nucleoli, and brisk mitotic activity (>10 mitoses/10 hpf) 2. **Growth pattern:** Solid sheets, micropapillary, and glandular structures with marked pleomorphism 3. **TP53 mutation:** Present in ~96% of cases — a defining molecular feature 4. **Tubal origin:** Often arises from fallopian tube epithelium (STIC: serous tubal intraepithelial carcinoma) **High-Yield:** HGSC accounts for ~70% of epithelial ovarian cancers and is the most chemosensitive histotype, but carries the worst prognosis when diagnosed at advanced stage (80% present as stage III/IV). ## Why This Patient Has HGSC - **Postmenopausal age** rules out most benign tumors - **Massive CA-125 elevation** (850 U/mL) is highly specific for malignancy; benign cystadenomas rarely exceed 100 U/mL - **Ascites + omental caking + peritoneal nodules** = stage IIIC disease (peritoneal spread beyond pelvis) - **Solid-cystic heterogeneous mass** on imaging suggests high-grade malignancy, not simple adenoma **Clinical Pearl:** In a postmenopausal woman with a complex ovarian mass, ascites, and CA-125 >100 U/mL, assume epithelial ovarian cancer until proven otherwise. HGSC is the most common and most likely diagnosis. ## Management Implications **Tip:** Staging laparotomy/laparoscopy with optimal cytoreduction followed by platinum-taxane chemotherapy (carboplatin + paclitaxel) is the standard of care. BRCA1/2 testing and consideration of PARP inhibitors (maintenance therapy) are now standard in advanced HGSC.