## Investigation of Choice for Locoregional Staging in Gastric Carcinoma ### Why Endoscopic Ultrasound (EUS) is Optimal **Key Point:** EUS is the gold standard for assessing T-stage (depth of tumor invasion) and N-stage (regional lymph node involvement) in gastric cancer. It provides superior resolution of the gastric wall layers and perigastric lymph nodes compared to cross-sectional imaging. **High-Yield:** EUS can: - Differentiate between T1a (mucosa), T1b (submucosa), T2 (muscularis propria), T3 (subserosa), and T4 (serosa/adjacent structures) - Identify regional lymph nodes (N1, N2) with >90% accuracy for nodes >3 mm - Guide fine-needle aspiration (FNA) for cytological confirmation of involved nodes - Assess resectability in early-stage disease ### Role of Other Investigations | Investigation | Role in Gastric Cancer | Limitation | |---|---|---| | **CT chest/abdomen** | Detects distant metastases (M-stage), assesses peritoneal involvement | Poor resolution for T-stage and small regional nodes (<1 cm) | | **PET-CT** | Identifies distant metastases and FDG-avid nodes | Low sensitivity for small primary tumors and T-staging | | **Diagnostic laparoscopy** | Detects peritoneal/liver metastases missed on imaging | Invasive; not first-line for locoregional staging | **Clinical Pearl:** In this patient with histologically confirmed adenocarcinoma, EUS should be performed before CT staging to guide treatment decisions (surgery vs. neoadjuvant chemotherapy). **Mnemonic — EUS in Gastric Cancer (T-N-E):** - **T** = Tumor depth (T-stage) - **N** = Node involvement (N-stage) - **E** = Endoscopic approach (no radiation, real-time assessment) **Warning:** EUS is operator-dependent and may be limited by gastric stenosis or inability to pass the scope; in such cases, CT or MRI becomes the alternative.
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