A 62-year-old woman undergoes upper GI endoscopy for chronic epigastric pain and anaemia. Endoscopy shows a 3 cm submucosal bulge in the gastric fundus with intact overlying mucosa and a central dimple. Biopsy of the mucosa is non-diagnostic. What is the most appropriate next investigation to establish the diagnosis?

Explanation

## Investigation of Choice for Submucosal Gastric Lesions **Key Point:** Endoscopic ultrasound (EUS) with fine-needle aspiration (FNA) is the investigation of choice for submucosal lesions of the stomach because it provides real-time visualization of the lesion's layer of origin, size, echogenicity, and allows tissue sampling via FNA. ### Clinical Presentation Clue: "Submucosal Bulge with Intact Mucosa" The description of a submucosal bulge with intact overlying mucosa and a central dimple is classic for a **gastrointestinal stromal tumour (GIST)** or other submucosal neoplasm (leiomyoma, schwannoma). Standard endoscopic biopsy fails because the lesion arises *below* the mucosa. ### Why EUS is Superior for Submucosal Lesions | Feature | EUS ± FNA | CT Abdomen | Repeat Endoscopy | Barium Meal | | --- | --- | --- | --- | --- | | **Visualizes layer of origin** | ✓ (high resolution) | ✗ | ✗ | ✗ | | **Tissue diagnosis** | ✓ (FNA) | ✗ (imaging only) | ✗ (mucosa only) | ✗ | | **Assesses echogenicity/vascularity** | ✓ | Limited | ✗ | ✗ | | **Risk stratification (size, mitotic rate)** | ✓ | ✓ | ✗ | ✗ | | **Real-time guidance** | ✓ | ✗ | ✗ | ✗ | ### EUS Findings in Common Submucosal Lesions ```mermaid flowchart TD A[Submucosal lesion on endoscopy]:::outcome --> B[EUS assessment]:::action B --> C{Echogenicity & vascularity?}:::decision C -->|Hypoechoic, homogeneous, avascular| D[Leiomyoma/Schwannoma]:::outcome C -->|Hypoechoic, heterogeneous, vascular| E[GIST - FNA for confirmation]:::action C -->|Hyperechoic, small| F[Lipoma]:::outcome E --> G[Immunohistochemistry: CD117, DOG1]:::action G --> H[Risk stratification: size + mitotic rate]:::action ``` **High-Yield:** EUS-FNA is diagnostic gold standard for submucosal lesions because: - Identifies the exact layer of origin (muscularis propria vs. submucosa) - Allows tissue diagnosis when endoscopic biopsy fails - Guides risk stratification for GISTs (size, echogenicity, vascularity) - Directs management (endoscopic resection vs. surgical resection) **Clinical Pearl:** The "central dimple" described in this case is a characteristic finding in GISTs and suggests the lesion arises from the muscularis propria. EUS-FNA with immunohistochemistry (CD117, DOG1) confirms the diagnosis. **Mnemonic:** **GIST** = **G**astrointestinal **I**stromal **S**ubmucosal **T**umour — always think EUS for submucosal lesions. **Warning:** ~~Repeat endoscopic biopsy will fail again~~ because the lesion is submucosal; ~~CT is useful for staging but not tissue diagnosis~~; ~~barium meal is obsolete for this indication~~. [cite:Robbins 10e Ch 17]