Benign gastric tumors - of epithelial and mesenchymal origin. Stromal tumors - GIST
The list of benign gastric tumors is:
- Gastric polyps
- Fundic gland polyps
- Gastric adenoma
- Lipomas
- Leiomyomas
Two potentially malignant ones are:
- Carcinoid tumour
- Gastrointestinal stromal tumor (GIST)
Gastric polyps (epithelial tumour)
- These are nodules or masses that project above the mucosa
- May be as a result of hyperplasia, inflammation, ectopia or neoplasia
- There are different types of polyps
- Inflammatory and hyperplastic polyps
- Most common by far, affect those 50-60
- Usually have chronic gastritis with H.pylori
- Frequently multiple, stable, smooth, ovoid and less than 1cm
- Microscopically polyps have irregular, cystically dilated foveolar glands and lamina propria is edematous
- Polyps larger than 1.5cm have increase risk of dysplasia, a precancerous in situ lesion
- Fundic gland polyps
- Sporadic and in persons with familial adenomatous polyposis (FAP)
- No neoplastic potential
- Occur as a result of proton pump inhibitor use
- May be asymptomatic, or cause vomiting and nausea
- Gastric adenoma
- 10% of cases, occur in background of chronic gastritis with atrophy
- Risk of adenocarcinoma development, bigger polyp, bigger risk
- (see gastric adenoma section below)
Gastric lipoma (mesenchymal tumour)
- Derived from fat tissue, they are rare (less than 1% of gastric neoplasms)
- May present with upper GI bleeding, dyspepsia or gastric obstruction
- Histology shows adipose cells with fibrous capsule
Gastric Leiomyoma (mesenchymal tumour)
- Rare, asymptomatic, generally found incidentally
- Derived from smooth muscle of muscularis propria or lamina muscularis mucosa of stomach
Carcinoid tumour (neuroendocrine tumour)
- Of neuroendocrine origins (neuroendocrine cells of the gut mucosa)
- Most are asymptomatic however all have malignant potential and about 10% secrete hormones (most commonly serotonin, causing flushing, diarrhea, wheezing, abdominal cramps and peripheral edema).
- In the GI system, Carcinoid tumours are most common in the appendix or small intestines.
- Known as carcinoid as they are slower growing than carcinomas
- They created small yellow polypoid lesions that can cause kinking of bowel and obstruction. Histologically the are composed of islets, strands and glands.
- The most important prognostic factor is the location
- Foregut - stomach + proximal duodenum rarely metastasize and are cured by resection
- Midgut - jejunum + ileum tend to be more aggressive
- Hind gut - appendix and colorectum - almost always benign, although rectal forms generally produce polypeptide hormones
Gastrointestinal stromal tumour (GIST) (mesenchymal tumour)
- Most common mesenchymal tumour of the abdomen, more than half in the stomach
- More common in males - 80% have mutation of tyrosine kinase c-KIT gene