40. Malignant tumors of the stomach

Malignant tumours of the stomach

Gastric adenocarcinoma is the commonest malignant gastric tumour. Risk factors include H. pylori, chronic atrophic gastritis, intestinal metaplasia, smoking, high-salt preserved foods, family history and hereditary cancer syndromes.
Other malignant tumours include gastric lymphoma, GIST and neuroendocrine neoplasms. Diffuse-type carcinoma may be associated with CDH1 mutations and signet-ring cells.

Lauren classification divides adenocarcinoma into intestinal and diffuse types. Intestinal type forms glands and is associated with chronic gastritis/metaplasia; diffuse type infiltrates the wall and may cause linitis plastica.
Spread occurs by direct invasion, lymphatic dissemination and haematogenous metastasis, particularly to liver and peritoneum.
Classic metastatic signs include Virchow node (left supraclavicular), Sister Mary Joseph nodule (umbilical), Krukenberg tumour (ovarian metastasis) and Blumer shelf (pelvic peritoneal deposit).

Early gastric cancer may be asymptomatic. Symptoms include persistent dyspepsia, epigastric pain, early satiety, anorexia, weight loss, nausea, vomiting and iron-deficiency anaemia.
Advanced disease may cause palpable epigastric mass, ascites, jaundice, gastric outlet obstruction, haematemesis or melaena.
Alarm features include progressive symptoms, weight loss, anaemia, vomiting, dysphagia, palpable mass and family history.

Upper GI endoscopy with multiple biopsies is the diagnostic standard. Histology confirms type and grade; test relevant biomarkers (e.g. HER2, mismatch repair/MSI, PD-L1 and CLDN18.2 where applicable) to guide systemic therapy.
Contrast CT chest/abdomen/pelvis stages disease. Endoscopic ultrasound assesses depth and regional nodes in selected cases. Diagnostic laparoscopy with peritoneal washings is considered for potentially resectable locally advanced disease because CT can miss peritoneal spread.
Stage by TNM. Assess nutritional status, performance status and cardiopulmonary fitness. Differential includes peptic ulcer, gastritis, pancreatic disease, lymphoma and benign gastric tumours.

Early mucosal lesions may be suitable for endoscopic submucosal dissection in carefully selected patients.
Resectable disease is treated with gastrectomy (subtotal or total depending on site and margins) plus appropriate lymphadenectomy, often combined with perioperative chemotherapy or adjuvant treatment according to stage and regional guidelines.
Metastatic/unresectable disease is treated with biomarker-directed systemic therapy, chemotherapy, immunotherapy or targeted agents as appropriate. Palliative interventions address obstruction, bleeding, pain and nutrition.
Complications include bleeding, perforation, obstruction, malnutrition, peritoneal carcinomatosis and recurrence. Post-gastrectomy complications include anastomotic leak, dumping syndrome, bile reflux, micronutrient deficiencies and weight loss.