Explore common tumours of the GI tract, including oesophageal adenocarcinoma, gastric MALT lymphoma, colorectal polyps, and GIST. Learn about risk factors, path
Oesophageal Tumours 1. Oesophageal Adenocarcinoma - Demographics: White males; 7× more common in men; highest in developed Western countries. - Risk Factors: Barrett oesophagus, chronic GERD, documented dysplasia, tobacco, obesity, radiation. - Protective Factors: Fruits and vegetables. - Pathogenesis: Accumulation of genetic and epigenetic changes (TP53, chromosomal abnormalities). - Morphology: - Location: Distal 1/3 of oesophagus; may invade gastric cardia. - Gross: Early flat/raised patches; late exophytic mass or ulcerated. - Microscopy: Mucin-producing, gland-forming tumour; Barrett oesophagus adjacent to tumour. 2. Oesophageal Squamous Cell Carcinoma (SCC) - Demographics: Adults 45 yrs; males 4× more; higher incidence in African Americans. - Risk Factors: Alcohol and tobacco (synergistic), poverty, nutritional deficiencies, caustic injury, achalasia, Plummer-Vinson syndrome, hot beverages, HPV (high-risk regions). - Morphology: - Location: Middle 1/3 of oesophagus. - Gross: Grey-white plaque-like thickenings; later polypoid/obstructing or ulcerated. - Microscopy: Moderately to well differentiated; variants include verrucous and spindle cell. - Spread: Rich submucosal lymphatics lead to circumferential and longitudinal spread (skip lesions). - Lymph Node Metastases: - Upper 1/3: Cervical nodes. - Middle 1/3: Mediastinal, paratracheal, tracheobronchial. - Lower 1/3: Gastric and coeliac nodes. Gastric Tumours 1. Gastric Polyps - Inflammatory & Hyperplastic Polyps: Associated with chronic gastritis; risk of dysplasia increases with size. - Gastric Adenomas: Arise in background of chronic gastritis with intestinal metaplasia; premalignant; require complete excision. 2. Gastric Adenocarcinoma - Aetiology: H. pylori (most common), chronic atrophic gastritis, EBV infection. - Histologic Types: - Intestinal Type: Bulky, discrete, gland-forming cells. - Diffuse Type: Signet ring cells; diffuse infiltration leading to Linitis Plastica ("leather bottle stomach"). 3. Gastric MALT Lymphoma - Derived from mucosa-associated lymphoid tissue (MALT) induced by chronic H. pylori gastritis. - H. pylori eradication can lead to tumour regression in early stages. 4. Gastrointestinal Stromal Tumour (GIST) - Most common mesenchymal tumour of the abdomen; arises from Interstitial Cells of Cajal. - Mutations: Activating mutations in c-KIT or PDGFRA tyrosine kinases. - Treatment: Tyrosine kinase inhibitors (e.g., Imatinib). Colorectal Tumours 1. Colorectal Polyps - Non-Neoplastic: Inflammatory, Hamartomatous (Peutz-Jeghers), and Hyperplastic (no malignant potential). - Neoplastic (Adenomas): Characterized by cytologic dysplasia; precursors to adenocarcinoma. - Sessile Serrated Adenomas: Lack cytologic dysplasia but carry malignant potential. 2. Genetic Syndromes - Familial Adenomatous Polyposis (FAP): APC mutation (Chr 5); 100 polyps; cancer risk 100% by age 30; Chromosomal Instability (CIN) pathway. - Hereditary Non-Polyposis Colorectal Cancer (HNPCC/Lynch): DNA mismatch repair gene mutations (MLH1, MSH2); Microsatellite Instability (MSI) pathway. 3. Colorectal Adenocarcinoma - Prognostic Factors: 1. Depth of invasion (T stage) 2. Lymph node metastases (N stage). Appendix Tumours - Carcinoid: Most common; usually incidental at distal tip; almost always benign. - Adenocarcinoma: Can lead to intraperitoneal seeding; mimics mucinous ovarian tumours in women. - Pseudomyxoma Peritonei: Advanced complication where the abdomen fills with mucin; managed by debulking but often fatal. Summary Table Tumour Location Key Feature --- --- --- Oesophageal Adenocarcinoma Distal 1/3 Barrett oesophagus; TP53 mutation Oesophageal SCC Middle 1/3 Alcohol/Tobacco; HPV (some regions) Gastric Adenocarcinoma Stomach H. pylori; Signet ring cells GIST Stomach c-KIT mutation; Cajal cells Carcinoid Small Intestine Most aggressive site for carcinoids FAP Colon APC mutation; 100 polyps HNPCC Colon Mismatch repair defect; MSI