PA23.1-9 | Gastrointestinal Tract — Glossary

The earliest morphologically identifiable precursor lesion in the adenoma-carcinoma sequence — focal clusters of dysplastic crypts visible on magnifying colonoscopy; considered a biomarker of field-effect carcinogenesis in the colon.

A motility disorder of the oesophagus characterised by failure of the lower oesophageal sphincter to relax, causing dysphagia for both solids and liquids simultaneously and chronic food stasis; a risk factor for oesophageal SCC.

Transmural inflammation of the appendix, initiated by luminal obstruction leading to increased pressure, mucosal ischaemia, and bacterial invasion; the commonest cause of acute surgical abdomen.

The stepwise molecular and morphological progression from normal colonic epithelium through benign adenomatous polyps to invasive adenocarcinoma, driven by sequential accumulation of mutations over 10–15 years; the biological basis for colonoscopic surveillance.

A benign neoplastic glandular lesion of the colonic mucosa with genuine malignant potential; classified as tubular, tubulovillous or villous based on the proportion of villous architecture.

An infiltrative growth pattern causing circumferential, ring-like narrowing of the oesophageal or colonic lumen; radiologically produces the 'apple-core' or 'rat-tail' appearance on barium studies.

Tumour suppressor gene on chromosome 5q21 encoding a scaffolding protein that targets β-catenin for degradation; the gatekeeper mutation initiating the chromosomal instability pathway in both sporadic CRC and FAP.

The principal alkaloid of areca nut; stimulates fibroblasts, inhibits collagen degradation, and causes subepithelial fibrosis (OSMF); IARC Group 1 carcinogen.

Chronic gastritis caused by autoantibodies against parietal cells and intrinsic factor; affects the gastric corpus/fundus, causing achlorhydria, pernicious anaemia (vitamin B12 deficiency), and increased gastrin levels; associated with gastric carcinoma and carcinoid risk.

Replacement of normal stratified squamous epithelium of the lower oesophagus by specialised intestinal metaplasia (columnar epithelium with goblet cells) as an adaptive response to chronic GERD; the main precursor of oesophageal adenocarcinoma.

A histological grading system for SCC based on degree of differentiation: Grade I (well-differentiated, abundant keratin pearls) through Grade III (poorly differentiated, rare pearls, marked pleomorphism).

A virulence protein injected by H. pylori into gastric epithelial cells; activates signalling cascades promoting inflammation, cell proliferation, and carcinogenesis.

An oncofetal glycoprotein re-expressed in colorectal carcinoma; used clinically NOT for diagnosis or screening but for post-operative monitoring of recurrence — a rising CEA after curative resection is the earliest indicator of disease return.

Full-thickness epithelial dysplasia without breach of the basement membrane; equivalent to high-grade dysplasia; the immediate precursor to invasive carcinoma.

A granuloma with central amorphous eosinophilic necrosis (caseous necrosis); the histological hallmark of tuberculosis that distinguishes it from the non-caseating granulomas of Crohn disease and sarcoidosis.

A molecular phenotype characterised by widespread chromosomal gains and losses (aneuploidy) due to defects in chromosomal segregation; drives ~85% of sporadic CRC through the APC→KRAS→SMAD4→TP53 pathway.

The gross mucosal pattern in Crohn disease produced by intersecting longitudinal and transverse fissures surrounding oedematous mucosal islands, resembling a cobblestone road.

Gross appearance of Crohn disease: islands of oedematous surviving mucosa separated by linear or fissuring ulcers, resembling cobblestones.

Gluten-sensitive enteropathy in which gliadin triggers an immune-mediated destruction of small intestinal villi (villous atrophy), diagnosed by anti-tTG/EMA serology and duodenal biopsy; responds to gluten-free diet.

The sequential pathological progression: H. pylori infection → chronic active gastritis → atrophic gastritis → intestinal metaplasia → dysplasia → intestinal-type gastric carcinoma.

Extension of mesenteric adipose tissue over the serosal surface of the bowel wall; a gross hallmark of transmural Crohn disease inflammation.

A chronic immune-mediated IBD characterised by transmural inflammation, skip lesions, non-caseating granulomas, fistulae, and cobblestone mucosa affecting any GI segment from mouth to anus.

Collection of neutrophils within a colonic crypt; the histological hallmark of acute ulcerative colitis, reflecting active mucosal inflammation.

A functional absorptive test using oral pentose sugar (D-xylose) that is absorbed passively by intestinal mucosa without pancreatic enzymes; low urinary excretion indicates mucosal disease rather than pancreatic insufficiency.

Reactive fibrous stromal proliferation around invasive carcinoma; seen at the edges of malignant ulcers and in the stroma of invasive carcinomas as dense collagen bands.

A gastric carcinoma composed of individually infiltrating cells (signet-ring cells) without gland formation; produces linitis plastica grossly; associated with E-cadherin loss.

A histological feature characteristic of colorectal adenocarcinoma: necrotic cellular and nuclear debris within tumour gland lumina on H&E staining, helping distinguish CRC from other gland-forming adenocarcinomas at metastatic sites.

A pathological staging system for colorectal carcinoma: A = confined within bowel wall (>90% 5-yr survival), B = through wall, node-negative (65–75%), C = any nodal involvement (30–40%), D = distant metastases (<5%).

Disordered epithelial growth with nuclear atypia, loss of cellular polarity, and abnormal maturation, confined within the epithelium; classified as low-grade or high-grade depending on extent of full-thickness involvement.

A transmembrane glycoprotein mediating epithelial cell-cell adhesion; loss of E-cadherin (via CDH1 mutation or promoter methylation) is the hallmark of diffuse-type gastric carcinoma, allowing tumour cells to dissociate and infiltrate.

Thickening and hyalinisation of arterial walls seen in the fibrotic base of chronic peptic ulcer; prevents vessel contraction when eroded, contributing to haemorrhage.

A rare but serious T-cell lymphoma arising in the small intestine as a long-term complication of uncontrolled coeliac disease; associated with refractory or poorly managed gluten exposure.

A red velvety patch on oral mucosa with the highest premalignant potential of all oral lesions; ~90 % show severe dysplasia or carcinoma in situ on biopsy.

A calcified, hardened mass of faecal material that can obstruct the appendiceal lumen, initiating the pathogenetic cascade of acute appendicitis.

An autosomal dominant syndrome caused by germline APC mutation, characterised by hundreds to thousands of colorectal adenomas appearing in adolescence, with near-certain progression to CRC by age 40 if untreated.

The luminal surface zone of a peptic ulcer floor: fibrin and dead cell debris with neutrophils visible on H&E as a bright eosinophilic smear.

The concept that a carcinogen (e.g. tobacco) exposes an entire mucosal field simultaneously, creating multiple independent foci of dysplasia and explaining synchronous second primary tumours in the aerodigestive tract.

A non-invasive colorectal cancer screening test that detects haem-peroxidase activity in stool from occult bleeding; a positive result prompts colonoscopy; annual use in average-risk adults ≥50 years reduces CRC mortality.

An exophytic, cauliflower-like gross pattern of carcinoma projecting into the lumen, commonly seen in oesophageal and colorectal SCC.

Advanced appendicitis with ischaemic necrosis of the appendiceal wall, producing green-black discolouration and high risk of perforation.

Narrowing of the pyloric channel due to fibrosis (scarring) from chronic peptic ulcer disease, causing recurrent vomiting of undigested food, succussion splash, and hypochloraemic hypokalaemic metabolic alkalosis.

Transverse, circumferential ulcer running perpendicular to the long axis of the bowel — the pathognomonic gross feature of ulcerative intestinal tuberculosis.

Mucin-secreting columnar epithelial cells shaped like a goblet; their presence in oesophageal biopsy defines intestinal metaplasia (Barrett oesophagus) and is highlighted by alcian blue stain.

Zone 3 of the peptic ulcer floor: proliferating capillary endothelial buds and fibroblasts embedded in oedematous stroma — the hallmark of active healing.

The third histological zone of a chronic peptic ulcer, consisting of newly formed capillaries (angiogenesis) and proliferating fibroblasts with mixed inflammatory cells; represents active wound healing.

A commercially prepared mixture of tobacco, areca nut, slaked lime, and flavourings; a smokeless tobacco product widely used in India and a major risk factor for oral cancer and OSMF.

A microaerophilic, gram-negative, spiral-shaped bacterium that colonises gastric mucus; produces urease and cytotoxins (CagA, VacA); the commonest cause of peptic ulcer disease and a WHO Group 1 gastric carcinogen.

A subset of head and neck SCC driven by human papillomavirus types 16/18 (E6/E7 oncoproteins disrupt p53 and Rb); arises in tonsil and base of tongue; typically younger, non-smoking patients; better prognosis than tobacco-associated SCC.

Abnormal firmness or hardening of tissue due to fibrosis or tumour infiltration; palpable induration of the margins of an oral ulcer is a key clinical sign distinguishing carcinoma from benign inflammatory ulcer.

Replacement of one type of normal epithelium by intestinal-type columnar epithelium containing goblet cells; in the oesophagus, it defines Barrett oesophagus.

Mycobacterial infection of the bowel, most commonly involving the ileocaecal region; produces either transverse ulcerative disease or hyperplastic fibrotic thickening with caseating granulomas in all bowel layers.

A gastric carcinoma that forms recognisable glandular structures on H&E, arising in a background of intestinal metaplasia; associated with H. pylori infection and environmental factors.

CD8+ T lymphocytes within the intestinal epithelium; >25 per 100 enterocytes is the earliest histological change in coeliac disease and a component of Marsh grade 1 lesions.

Longitudinal tumour extension within the submucosal lymphatics of the oesophagus, often well beyond the visible margin of the tumour; necessitates wide resection margins at surgery.

A concentric whorl of squamous cells progressively undergoing keratinisation toward the centre; the histological hallmark of well-differentiated squamous cell carcinoma.

Bilateral ovarian metastases, most commonly from gastric carcinoma (signet-ring cells), spread by transcoelomic seeding through the peritoneal cavity; characterised histologically by signet-ring cells within a cellular (desmoplastic) ovarian stroma.

A histological classification of gastric adenocarcinoma into intestinal type (gland-forming, H. pylori-associated, Correa cascade) and diffuse type (non-cohesive, signet-ring cells, E-cadherin loss); they differ in epidemiology, pathogenesis, and prognosis.

A clinical term for a white patch on oral mucosa that cannot be scraped off and has no other identifiable cause; histologically may show hyperkeratosis alone (low risk) or epithelial dysplasia (moderate-to-high risk for SCC transformation).

Gross appearance of diffuse infiltrating gastric carcinoma in which tumour cells permeate all layers of the stomach wall, causing diffuse thickening, rigidity, and a leather-bottle appearance; typically diffuse Lauren type.

An autosomal dominant cancer predisposition syndrome caused by germline MMR gene mutations (MLH1, MSH2, MSH6, PMS2), characterised by MSI-H colorectal carcinoma (often right-sided, mucinous) and elevated risk of endometrial, ovarian and other carcinomas.

Failure of the small intestine to adequately absorb one or more nutrients, presenting with steatorrhoea, weight loss, and nutritional deficiencies; caused by mucosal, luminal, or structural defects.

Accumulation of insertion/deletion errors at short repetitive DNA sequences (microsatellites) throughout the genome, resulting from defective mismatch repair; the molecular hallmark of Lynch syndrome and ~15% of sporadic CRC.

A DNA repair system that corrects base-pair mismatches and insertion/deletion loops arising during replication; key genes include MLH1, MSH2, MSH6, PMS2; loss leads to microsatellite instability.

A colorectal adenocarcinoma subtype with >50% of the tumour consisting of extracellular mucin pools; associated with MSI-H and Lynch syndrome; classified as poorly differentiated (G3) by default.

A protective unstirred gel layer secreted by gastric surface epithelium that traps bicarbonate, neutralises back-diffusing H+ ions, and prevents peptic digestion of the mucosa.

A thin smooth muscle layer at the base of the mucosa; invasion beyond this layer defines malignant transformation of a dysplastic polyp into adenocarcinoma.

The classic gross morphological appearance of left-sided colorectal carcinoma — a circumferential annular constricting tumour that encircles the bowel wall and narrows the lumen, producing obstruction and altered stool calibre.

A granuloma composed of epithelioid macrophages and giant cells without central necrosis; key microscopic feature of Crohn disease (and sarcoidosis).

A chronic progressive premalignant condition of the oral cavity caused by areca nut (arecoline), characterised by subepithelial fibrosis, epithelial atrophy, trismus, and 7–13 % malignant transformation rate.

A mucosal break extending at least into the submucosa, caused by acid-pepsin imbalance; characterised by a clean, punched-out base with converging folds and a four-zone histological floor.

A condition in which mucosal defects extending through the muscularis mucosae develop in the stomach or duodenum due to excess aggressive factors (acid, H. pylori, NSAIDs) overcoming mucosal defensive mechanisms.

A macrocytic megaloblastic anaemia resulting from vitamin B12 deficiency due to loss of intrinsic factor (from autoimmune parietal cell destruction in Type A gastritis); a risk factor for gastric carcinoma.

An autosomal dominant hamartomatous polyposis syndrome caused by STK11/LKB1 mutation, characterised by GI hamartomatous polyps and mucocutaneous melanin pigmentation; elevated CRC risk but proceeds through a non-adenomatous pathway.

A triad of iron-deficiency anaemia, dysphagia (from oesophageal web), and koilonychia (spoon nails); causes mucosal atrophy predisposing to oesophageal SCC; more common in women.

The gross morphological appearance of right-sided colorectal carcinoma — a large exophytic, cauliflower-like mass projecting into the wide cecal/ascending colonic lumen; bleeds occultly but rarely obstructs.

Septic emboli spreading via the portal venous system from an abdominal infective source (e.g., perforated appendix) to produce multiple hepatic abscesses.

Fibro-inflammatory stricturing of intra- and extrahepatic bile ducts; strongly associated with ulcerative colitis (70% of PSC patients have IBD) and carries risk of cholangiocarcinoma.

Dysphagia beginning with solids and advancing to semi-solids then liquids over weeks to months; pathognomonic of mechanical luminal narrowing (carcinoma, stricture) as opposed to the simultaneous solid-and-liquid dysphagia of functional obstruction (achalasia).

Lipid mediators synthesised by COX-1 in gastric mucosa that stimulate mucus/bicarbonate secretion, maintain mucosal blood flow, and inhibit acid secretion; their depletion by NSAIDs is the primary mechanism of NSAID-induced gastropathy.

An island of surviving inflamed mucosa surrounded by ulceration in ulcerative colitis; grossly resembles a true polyp but is not a neoplasm.

Islands of regenerating mucosa surrounded by areas of ulceration in ulcerative colitis; they appear polypoid but are not neoplastic, representing mucosal remnants in a sea of ulceration.

Gross description of a benign peptic ulcer with sharply demarcated, perpendicular walls and a clean flat base, as if made by a cookie-cutter; contrasts with the heaped irregular margins of malignant ulcers.

Regenerating epithelium at the edge of a peptic ulcer with mildly enlarged but uniform nuclei and preserved architecture; must not be misinterpreted as dysplasia.

A multi-part test of vitamin B12 absorption assessing intrinsic factor dependence, ileal mucosal function, and bacterial overgrowth by sequential administration of labelled B12 with and without cofactors.

A tumour cell characteristic of diffuse-type gastric adenocarcinoma in which intracytoplasmic mucin accumulates and displaces the nucleus to the cell periphery, creating a signet-ring appearance on H&E.

A poorly differentiated CRC subtype in which single neoplastic cells contain large intracytoplasmic mucin vacuoles that displace the nucleus to the cell periphery, resembling a signet ring; carries the worst prognosis among CRC subtypes.

A subcutaneous periumbilical tumour nodule representing transcoelomic peritoneal metastasis, typically from gastric or ovarian carcinoma; indicates widespread intraperitoneal spread.

Segments of diseased bowel separated by intervening normal mucosa; pathognomonic of Crohn disease and absent in ulcerative colitis, which is continuous.

Excretion of excess fat in faeces (>7 g/day on a 100 g/day fat diet) due to malabsorption; stools are bulky, greasy, pale, and offensive.

Stage of appendicitis with transmural neutrophil infiltration, mucosal ulceration, and microabscess formation; the appendix is grossly swollen with fibrinous serosal exudate.

An intestinal enzyme that deamidates gliadin peptides; also the autoantigen targeted by anti-tTG IgA antibodies, the most sensitive first-line serological test for coeliac disease.

Life-threatening complication of severe UC (occasionally Crohn) in which transmural inflammation causes colonic dilatation >6 cm with risk of perforation; barium enema and colonoscopy are contraindicated.

A route of tumour dissemination in which malignant cells shed into the peritoneal cavity and implant on peritoneal surfaces, producing peritoneal carcinomatosis, malignant ascites, or Krukenberg tumours of the ovaries.

Inflammatory infiltrate extending through all layers of the bowel wall (mucosa to serosa); characteristic of Crohn disease and tuberculous enteritis, but NOT ulcerative colitis.

Restricted mouth opening due to fibrosis or muscle invasion; a key clinical feature of oral submucous fibrosis and advanced oral cancer invading the masticatory muscles.

A malabsorption syndrome endemic to tropical countries including India, characterised by partial villous atrophy and pan-nutrient deficiency; likely infectious in aetiology and treated with tetracycline and folate.

The most common colorectal polyp; composed of branching dysplastic tubular glands with a stalk; low risk of malignancy but transforms if dysplasia progresses and invasion occurs.

Isolated single tumour cells or clusters of <5 cells at the invasive front of colorectal carcinoma; an independent adverse prognostic factor now routinely reported in surgical pathology as it predicts lymph node metastasis and recurrence.

Large macrophages with engulfed erythrocytes, bacteria, and cellular debris seen in the Peyer's patches of typhoid fever; their accumulation causes the characteristic longitudinal ulcers.

A chronic immune-mediated IBD limited to the colon and rectum, with continuous mucosal inflammation, crypt abscesses, pseudopolyps, and a significantly elevated risk of colorectal cancer with long disease duration.

Enzyme produced by H. pylori that splits urea into ammonia and CO2, neutralising local gastric acid to allow bacterial survival and causing direct epithelial damage.

Adenoma with ≥80% villous frond architecture; typically sessile, large, found in the rectum, and carrying the highest malignant potential (~40%) among adenoma types.

Flattening and shortening of small intestinal villi reducing absorptive surface area; seen in coeliac disease, tropical sprue, and Whipple disease; graded by the Marsh classification.

Metastatic enlargement of the left supraclavicular lymph node from an intra-abdominal malignancy (most often gastric carcinoma); spread is via the thoracic duct. Palpable node is Troisier's sign.

A rare systemic bacterial infection by Tropheryma whipplei causing malabsorption; histologically characterised by PAS-positive macrophages stuffed with bacteria in the lamina propria of the small intestine.

A condition caused by a gastrin-secreting neuroendocrine tumour (gastrinoma), usually in the pancreas/duodenum, producing massively elevated acid output, multiple/recurrent peptic ulcers, and secretory diarrhoea.

A transcriptional activator in the Wnt signalling pathway; normally targeted for degradation by APC; when APC is lost, β-catenin accumulates in the nucleus and drives transcription of proliferative genes.