Gastric Cancer

Gastric cancer is defined by the malignant proliferation of surface epithelial cells (adenocarcinoma). This is the most common type of gastric cancer. Gastric cancer has been associated with several risk factors, including acanthosis nigricans (which is associated with increased risk of gastric cancer and colon cancer.

Subclassfied into intestinal or diffuse type based on Lauren’s classification

Gastric cancer has been divided into 2 types: Diffuse type and Intestinal type (more common)

Intestinal type (more common)

• Occurs in setting of chronic gastritis from H.pylori or autoimmune gastritis
• Smoking, Nitrosamine (smoked food Japanese) can also cause intestinal type gastric cacer
• Neoplastic gland formation are usually present in this type of cancer, and resemble intestinal epithelium (post metaplasia)
• Usually develop from intestinal metaplasia as precursor lesion due to (H.pylori, autoimmune) at the lesser curvature in older patients

Diffuse type

• This type of gastric cancer is less common and is characterized by Signet ring cells that diffusely infiltrate the gastric wall and desmoplasia wall thickening
• There is usually no neoplastic gland formation, younger patients
• Suprisingly, this cancer is not associated with intestinal metaplasia or nitrosasmine, H.pylori, Chronic Gastritis.
• Familial types with female predominance with E-cadherin gene implicated
• Linitis plastic (a morphological variant of this cancer) : this present as a thickened and leathery bottle like stomach. They usually infiltrate early through all layers and have a very poor prognosis.
• Desmoplasia may occur around a neoplasm, causing dense fibrosis around the tumor, or scar tissue (adhesions) within the abdomen after abdominal surgery. Desmoplasia is usually only associated with malignant neoplasms, which can evoke a fibrosis response by invading healthy tissue

Symptoms and Clinical Presentation:

• 90% Asx until late in course, Weight loss anorexia (typical of Cancer)
• Epigastric abdominal pain mimicking peptic ulcer
• Early satiety (get full easily when you eat)
• Fe deficiency anemia from ulcerated tumor
• Acanthosis Nigricans (Also in colon cancer)

Morphology of Gastric Carcinoma

• Growth Pattern: Exophytic, Flat, Excavated
• Sites of tumor: Pylorus/antrum (most common) > Cardia > body/fundus

Course and Progression:

• Metastasis to virchow’s (Sentinel) node (Supraclavicular node)- Virchow’s refer to Left SCN
• Krukenberg tumor: Bilateral metastasis to ovaries especially from diffuse type gastric carcinoma
• Sister Mary Joseph nodule – palpable nodule bulging into the periumbilicus as a result of metastasis of malignant cancer in the pelvis and abdomen
• MALToma:
  • A form of lymphoma involving the MALT, frequently of the stomach, but virtually any mucosal site can be afflicted
  • Is a cancer originating from B cells in the marginal zone of the MALT
  • Regress with treatment of Antibiotics against H pylori.

GASTROINTESTINAL STROMAL TUMOR (GIST)

Defined as mesenchymal tumor derived from the interstitial cells of Cajal (pacemaker cells). They can be located anywhere along the gastrointestinal tract but with 60% in the stomach, submucosal. They appear as Whorls and bundles of spindle shaped cells under the microscope. One of the diagnostic marker of these cells are their expression of  Cd117 (c-kit)