What are Gastric Masses and Submucosal Lesions (GIST)?
Gastric masses represent a diverse group of pathological conditions within the stomach, ranging from benign polyps to malignant tumors. Submucosal lesions (SMLs), in particular, are masses arising beneath the mucosal surface, often involving the muscularis propria or submucosa layers. Among the various submucosal lesions, Gastrointestinal Stromal Tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, primarily originating in the stomach.
Causes of Gastric Masses and Submucosal Lesions
Submucosal lesions arise from one of the three deeper layers of the gastric wall-submucosa, muscularis propria, or serosa. These can be benign or malignant and include:
- Gastrointestinal stromal tumors (GISTs)
- Leiomyomas
- Lipomas
- SchwannomasEctopic pancreas
- Vascular anomalies
GIST
GISTs originate from the interstitial cells of Cajal or their precursors. They are typically associated with mutations in KIT (CD117) or PDGFRA genes, which lead to uncontrolled cell proliferation. The risk of malignant behavior depends on tumor size, mitotic index, and anatomical location.
Symptoms of Gastric Masses and Submucosal Lesions
Most individuals with submucosal gastric lesions, including GISTs, are asymptomatic and diagnosed incidentally during imaging or endoscopy. Symptomatic cases may present with:
- Epigastric pain or fullness
- Gastrointestinal bleeding (occult or overt)
- Nausea or vomiting
- Anemia
- Early satiety
- Palpable abdominal mass (rare)
Large lesions may ulcerate into the gastric lumen or cause obstruction.
Diagnosis of Gastric Masses and Submucosal lesion (GIST)
Gastric masses and submucosal lesions (GIST) can be diagnosed by your healthcare provider by either of the following:
Endoscopy: Submucosal lesions appear as smooth, rounded elevations of the mucosa. Central ulceration or umbilication may suggest GIST.
Endoscopic Ultrasound (EUS): This is essential for characterizing the lesion's origin, echogenicity (the ability of tissues to reflect sound waves during an ultrasound examination ), and layer involvement. GISTs typically arise from the fourth layer (muscularis propria) and are hypoechoic and well-circumscribed.
ImagingCT scan or MRI:
- These are useful for assessing size, extra gastric extension, and metastasis.PET scan:
- This may help in evaluating metabolic activity and treatment response
- 4.Histopathology
- Definitive diagnosis requires tissue biopsy.
- Immunohistochemistry: Positive for KIT (CD117), DOG1, and CD34 in most GISTs.
Management of Gastric Masses and Submucosal lesion (GIST)
GIST Treatment
- Surgical resection: Primary modality for localized, resectable GISTs.
- Tyrosine kinase inhibitors (TKIs): These are the first-line adjuvant and neoadjuvant therapies for high-risk or metastatic GISTs.
- Ongoing surveillance is necessary due to recurrence risk.
Other Submucosal Lesions
- Benign lesions such as lipomas or ectopic pancreas may only require observation.
- Symptomatic or growing lesions typically require removal via endoscopic or surgical methods.
Prognosis of Gastric Masses and Submucosal lesion (GIST)
Prognosis of GISTs varies with risk stratification. Factors influencing outcomes include:
- Tumor size (>5 cm associated with higher risk)
- High mitotic rate
- Location (gastric GISTs have better prognosis than small intestine or rectal GISTs)
- Complete surgical excision with negative margins
