Gastric Cancer

Predominantly adenocarcinoma (over 90% of cases), subdivided into intestinal type (well differentiated, associated with Helicobacter pylori, chronic atrophic gastritis, and intestinal metaplasia) and diffuse type (poorly differentiated, containing signet ring cells, occurring in younger patients, carrying a worse prognosis, and linked to hereditary diffuse gastric cancer from CDH1 mutations).

Gastric lymphoma, typically MALT lymphoma and strongly H. pylori associated, and gastrointestinal stromal tumor (GIST, a KIT driven mesenchymal tumor) are separate entities arising in the stomach that follow different management pathways.

Early disease is frequently asymptomatic or produces only nonspecific dyspepsia and early satiety. Advanced disease presents with weight loss, epigastric pain, nausea and vomiting, dysphagia if the tumor involves the proximal stomach or gastroesophageal junction, GI bleeding with resulting iron deficiency anemia, and a palpable epigastric mass. Signs of metastatic spread include Virchow's node, a Sister Mary Joseph nodule at the umbilicus, Krukenberg tumor (ovarian metastasis), and Blumer's shelf detected on rectal examination (a pelvic peritoneal deposit).

Upper GI endoscopy with multiple biopsies confirms diagnosis and histological subtype. Staging uses CT chest, abdomen, and pelvis; endoscopic ultrasound for T and N staging; PET CT for distant disease; and staging laparoscopy with peritoneal washings, since peritoneal seeding is common and often occult on cross sectional imaging. HER2 testing is performed on the biopsy or resection specimen to guide targeted therapy eligibility. FBC and iron studies assess for anemia.

Differentials include peptic ulcer disease, gastritis, GIST, gastric lymphoma, and benign gastric polyps.

Resectable disease is treated with perioperative chemotherapy (FLOT regimen) combined with gastrectomy (subtotal or total, depending on tumor location) and D2 lymphadenectomy. Endoscopic resection is an option for very early T1a mucosal cancers meeting strict size and differentiation criteria. HER2 positive metastatic disease is treated with trastuzumab added to chemotherapy; HER2 negative metastatic disease receives platinum fluoropyrimidine chemotherapy, with immunotherapy (nivolumab) increasingly incorporated for PD-L1 positive tumors. MALT lymphoma localized to the stomach often regresses with H. pylori eradication alone if early stage; more advanced or non-regressing lymphoma requires oncology directed chemoimmunotherapy. GIST is managed with imatinib (a tyrosine kinase inhibitor) for unresectable or metastatic disease, and surgical resection with or without adjuvant imatinib for localized disease depending on risk stratification.

Referral: upper GI surgery and oncology multidisciplinary team for all confirmed adenocarcinoma; hematology for confirmed lymphoma; sarcoma or GIST specialist service for confirmed GIST.