A 48-year-old woman with Stage IIIC ovarian cancer is being counseled about sites of metastatic spread. Which is the most common site of peritoneal involvement in advanced ovarian cancer?

Explanation

## Sites of Metastatic Spread in Ovarian Cancer **Key Point:** The omentum and peritoneal surfaces are the most common sites of metastatic involvement in advanced ovarian cancer, reflecting the intraperitoneal route of dissemination characteristic of ovarian malignancies. ### Pattern of Spread in Ovarian Cancer | Site of Involvement | Frequency in Advanced Disease | Mechanism | |---|---|---| | Omentum and peritoneal surfaces | 70–80% | Direct exfoliation and transcoelomic spread | | Liver capsule and diaphragm | 20–30% | Peritoneal seeding; direct invasion | | Retroperitoneal lymph nodes | 40–50% | Lymphatic spread (pelvic and para-aortic nodes) | | Distant organs (lung, pleura) | 5–10% | Hematogenous or transdiaphragmatic spread | | Brain, bone | <1% | Late hematogenous spread; uncommon | **High-Yield:** Ovarian cancer spreads predominantly by **transcoelomic dissemination** — exfoliation of malignant cells into the peritoneal cavity, which then implant on peritoneal surfaces, the omentum, and visceral peritoneum. This is fundamentally different from the lymphatic-first spread seen in many other cancers [cite:Robbins 10e Ch 22]. ### Clinical Implications **Clinical Pearl:** The omentum is so frequently involved that **omentectomy** (removal of the greater omentum) is a standard component of cytoreductive surgery in advanced ovarian cancer. Omental caking (dense tumor infiltration) is a hallmark finding in Stage IIIC disease. **Warning:** Do not confuse peritoneal involvement (most common in ovarian cancer) with hematogenous spread to distant organs (lung, bone, brain), which is rare and occurs late. The pattern of spread is intraperitoneal first, then lymphatic, then hematogenous. ### Staging Correlation - **Stage I:** Confined to ovary/ovaries - **Stage II:** Pelvic extension - **Stage III:** Peritoneal involvement beyond pelvis (omentum, peritoneal surfaces) — **most common advanced stage at diagnosis** - **Stage IV:** Distant organ involvement (pleural effusion, liver parenchyma, lung) **Mnemonic:** **OPL** — Omentum (most common), Peritoneal surfaces, Lymph nodes (in order of frequency in advanced ovarian cancer).