## Staging Investigations in Gastric Cancer **Key Point:** Endoscopic ultrasound (EUS) is the gold standard for **T-staging** (depth of invasion) and **N-staging** (regional lymph nodes) in gastric cancer. It has superior resolution for assessing the muscularis propria and submucosa compared to other modalities. ### Role of Each Investigation | Investigation | Primary Role | Accuracy for T-stage | Accuracy for N-stage | When Used | |---|---|---|---|---| | **EUS with FNA** | Local invasion & regional LN assessment | 85–90% | 80–85% | **First-line for staging** | | **CT abdomen/pelvis** | Distant metastases, peritoneal involvement | 60–70% | 60–70% | Assess M-stage, guide resectability | | **PET-CT** | Distant metastases (bone, liver) | Variable | Poor | Detect occult metastases | | **MRI abdomen** | Soft tissue planes | 70–75% | 65–70% | Alternative if EUS contraindicated | **High-Yield:** EUS is **mandatory** before surgery in gastric cancer to: 1. Confirm depth of invasion (T1–T4) 2. Assess regional lymph node involvement (N0–N3) 3. Guide extent of gastrectomy (subtotal vs. total) and lymphadenectomy **Clinical Pearl:** In this patient with a large antral lesion, EUS with FNA of suspicious nodes will provide tissue diagnosis of nodal involvement and prevent unnecessary extensive surgery if distant metastases are present. ### Why EUS is Superior for Local Staging - High-frequency ultrasound probe (7.5–20 MHz) provides excellent resolution of gastric wall layers - Can identify breach of muscularis propria (T2 vs. T1 distinction) - FNA capability allows cytologic confirmation of involved nodes - Real-time guidance for biopsy of suspicious nodes **Mnemonic:** **TUNE** for gastric cancer staging — **T**-stage (depth) and **N**-stage (nodes) → **U**se **E**ndoscopic ultrasound.
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