Gastric carcinoma: etiology and pathogenesis. Precancer. Microscopic & gross pathomorphology. Clinic-morphological methods of early diagnostics
There are three types of ‘gastric cancer’, Gastric carcinomas, lymphomas and GIST (may or may not be considered malignant). Here we consider Gastric carcinoma, specifically, Gastric adenocarcinoma, the most common malignancy of the stomach (90%) with early symptoms that resemble chronic gastritis.
Gastric adenocarcinoma is up to 20 times higher in Japan, Chile, Costa Rica and Eastern Europe. Areas like Japan do mass endoscopic screening programs to identify early gastric cancer.
Etiology and pathogenesis
- Has a genetic component (loss of E-cadherin function with mutation of CDH1 gene, in the diffuse type)
- Association with H. pylori which promotes chronic gastritis, conferring increased risks
- 10% of gastric adenocarcinomas are associated with Epstein-Barr virus
Gastric adenocarcinomas can be classified based on location as well as morphology. We separate them into intestinal and diffuse types. Diffuse gastric cancers have an infiltrative growth pattern with discohesive cells and large mucin vacuoles that create a signet ring cell morphology. These tumours invoke desmoplastic reactions that stiffen gastric wall and can cause thickened wall known as linitis plastica. Meanwhile intestinal type adenocarcinoma grow along cohesive fronts to form an exophytic mass or an ulcerative tumour.
Gross: intestinal-type gastric adenocarcinoma. A 7 cm fungating, ulcerated tumour in the antrum with raised, rolled (heaped-up) edges, unlike the flat margins of a benign peptic ulcer.
Image: “Gastric Adenocarcinoma (138614024)” by Ed Uthman from Houston, TX, USA, CC BY 2.0, via Wikimedia Commons.
Precancer lesion
- There is no precancerous lesion for the diffuse type
- The intestinal type is preceded by a dysplastic lesion with adenomas. It is closely associated with atrophic gastritis and intestinal metaplasia
The depth of invasion and extent of metastasis remain the most powerful indicator of prognosis. Cancer limited to the mucosa and submucosa (early gastric cancer) has a high survival rate.
Remember: classic signs of spread: Virchow node (left supraclavicular lymph node), Sister Mary Joseph nodule (periumbilical), Krukenberg tumour (bilateral ovarian metastases with signet ring cells) and a Blumer shelf (deposit in the rectovesical/rectouterine pouch).
Early diagnosis is via Gastroscopic exam, later diagnosis with upper GI X-ray or CT. Recent advances in china have looked at a breathalyzer style breath test which seems to be able to identify stomach cancer based on exhaled chemicals.