Specialty Guide · Path-iQ Global Pathology Review
Gastrointestinal pathology is the largest subspecialty by specimen volume in most anatomic pathology departments worldwide. The average endoscopy unit generates hundreds of biopsy specimens per week — Barrett's surveillance, colorectal cancer screening polyps, IBD activity grading, coeliac disease assessment, and Helicobacter pylori diagnosis — each requiring accurate histological interpretation to guide clinical management.
Barrett's oesophagus (BO) is defined as the replacement of squamous epithelium in the distal oesophagus by metaplastic columnar epithelium, predisposing to oesophageal adenocarcinoma (OAC). The histological grading of dysplasia in Barrett's is the principal determinant of endoscopic surveillance intervals and treatment decisions.
| Histological Category | Morphological Features | Cancer Risk (annual) | Management |
|---|---|---|---|
| Non-dysplastic Barrett's (NDBO) | Goblet cell metaplasia; no nuclear atypia; preserved surface maturation | 0.1–0.3% per year | Surveillance endoscopy every 3–5 years (BSG/AGA guidelines) |
| Indefinite for dysplasia (IND) | Atypia present but unclear if neoplastic vs reactive/inflammatory; poor surface sampling | ~1% per year | Optimise acid suppression (PPI); repeat biopsy in 3–6 months |
| Low-grade dysplasia (LGD) | Nuclear enlargement, hyperchromasia, pseudostratification; surface involvement; preserved architecture | ~0.5–1% per year (confirmed LGD); up to 9% if expert-confirmed | Expert pathology confirmation; endoscopic eradication therapy (EET) or intensified surveillance every 6 months |
| High-grade dysplasia (HGD) | Marked nuclear atypia; loss of surface maturation; complex glandular architecture; no invasion through BM | ~6–7% per year risk of OAC | Endoscopic eradication therapy (RFA ± EMR); resection for nodular HGD |
| Intramucosal adenocarcinoma (IMC) | Invasion through basement membrane into lamina propria; no invasion of muscularis mucosae | ~2% lymph node metastasis risk | EMR/ESD curative if complete resection and no adverse features (LVI, SM invasion) |
| Submucosal adenocarcinoma (T1b) | Invasion into submucosa; SM1 (<500 µm) vs SM2–3 (>500 µm from muscularis mucosae) | SM1: ~8% LN met; SM2–3: 20–30% LN met | Oesophagectomy for SM2–3; curative endoscopy for SM1 if no adverse features |
The hallmark of Crohn's disease on biopsy is transmural, patchy, granulomatous inflammation. Specific histological features: non-caseating granulomas (present in ~50% of biopsies; hallmark when present), architectural distortion (cryptitis, crypt abscess, crypt atrophy), pyloric gland metaplasia, neural hyperplasia, and lymphoid aggregates extending through the bowel wall. Unlike UC, rectal sparing is common and discontinuous (skip lesion) involvement is characteristic. Upper GI involvement (oesophagus, stomach, duodenum) on biopsy confirms Crohn's over UC in ambiguous colitis.
| Histological Feature | Score | Significance |
|---|---|---|
| Acute inflammatory cell infiltrate (neutrophils) | 0–3 | Primary marker of active disease; neutrophils in lamina propria and crypts |
| Cryptitis (neutrophils in crypt epithelium) | 0–3 | Graded by proportion of crypts affected; cryptitis grade 1 = <10% of crypts |
| Crypt abscess | 0–3 | Neutrophil collection within crypt lumen; indicates significant acute activity |
| Mucin depletion | 0–3 | Goblet cell loss; reflects epithelial stress; correlates with inflammation severity |
| Surface epithelial integrity | 0–3 | Erosion or ulceration; mucosal barrier disruption |
| Chronic inflammatory infiltrate | 0–3 | Plasmacytosis, especially basal plasmacytosis (early/diagnostic marker of UC) |
| Crypt architectural irregularity | 0–3 | Branching, atrophy, distortion; marker of chronic, established disease |
Histological remission in UC is defined as no neutrophils in the epithelium or lamina propria — a more stringent endpoint than clinical or endoscopic remission. Multiple randomised controlled trials (VARSITY, ULTIVUE, LUCENT) now use histological remission as a key secondary endpoint, and it is increasingly used as a clinical treat-to-target goal in UC management.
| pT Stage | Depth of Invasion | 5-Year Survival |
|---|---|---|
| pTis | In situ: carcinoma within epithelium or invading lamina propria (no submucosal invasion) | >99% |
| pT1 | Invasion of submucosa (through muscularis mucosae but not into muscularis propria) | ~93% |
| pT2 | Invasion into but not through muscularis propria | ~85% |
| pT3 | Invasion through muscularis propria into pericolorectal tissues | ~70–75% |
| pT4a | Penetration of visceral peritoneum (tumour cells on serosal surface) | ~55% |
| pT4b | Direct invasion of adjacent organs or structures | ~40% |
| Type | Lauren Class | TCGA Molecular Subtype | Frequency | Key Features |
|---|---|---|---|---|
| Intestinal-type adenocarcinoma | Intestinal | CIN (chromosomal instability) | ~50% | Gland-forming; H. pylori-associated; distal/antral predominance; best prognosis; HER2 amplification in ~20% of intestinal-type |
| Diffuse-type adenocarcinoma | Diffuse | GS (genomically stable) | ~30% | Signet ring cells; linitis plastica pattern; CDH1/E-cadherin loss; hereditary diffuse gastric cancer (HDGC) when germline CDH1; worst prognosis |
| Mixed-type | Mixed | Mixed | ~15% | Features of both intestinal and diffuse; intermediate prognosis |
| EBV-associated | — | EBV (EBV-positive) | ~9% | Dense lymphocytic stroma; EBER ISH positive; PIK3CA mutation; high PD-L1 expression; proximal/fundic predominance; best immunotherapy response |
| MSI-H gastric cancer | Usually intestinal | MSI (microsatellite instable) | ~22% | MLH1 promoter hypermethylation (mostly sporadic); antral predominance; best pembrolizumab response; better overall prognosis |
| Marsh-Oberhuber Grade | Histological Features | Clinical Significance |
|---|---|---|
| Type 0 (Normal) | Normal villous architecture; <30 IEL/100 enterocytes | Coeliac disease very unlikely if IgA anti-TTG negative |
| Type 1 (Infiltrative) | Normal villi; ≥30 intraepithelial lymphocytes (IEL) per 100 enterocytes; no crypt hyperplasia | Elevated IEL alone: coeliac, NSAID injury, H. pylori, microscopic colitis overlap; serology required |
| Type 2 (Hyperplastic) | IEL ≥30; crypt hyperplasia; villous architecture preserved | Rare; refractory coeliac or other enteropathy |
| Type 3a (Partial villous atrophy) | IEL ≥30; crypt hyperplasia; partial villous atrophy (villi still present but shortened) | Coeliac on gluten-containing diet or early treatment response |
| Type 3b (Subtotal villous atrophy) | IEL ≥30; crypt hyperplasia; subtotal villous atrophy | Active coeliac disease; gluten challenge biopsy in equivocal cases |
| Type 3c (Total villous atrophy) | IEL ≥30; crypt hyperplasia; complete loss of villi; flat mucosa | Severe/untreated coeliac disease; refractory coeliac disease type I or II |
The Sydney System (updated 1994) provides a standardised framework for reporting gastric biopsy findings including H. pylori status, inflammation grade, atrophy, intestinal metaplasia, and special features. A minimum of five biopsies is required: two from the antrum (greater and lesser curvature), two from the corpus (greater and lesser curvature), and one from the incisura angularis — the site of the highest risk of intestinal metaplasia and dysplasia.
Intestinal metaplasia (IM) in the stomach is the most important precancerous lesion in the gastric carcinogenesis sequence (Normal → H. pylori gastritis → Atrophic gastritis → IM → Dysplasia → Carcinoma). Type III IM (incomplete, sulphomucin-containing) carries higher malignant risk than type I (complete, sialomucin). The OLGA (Operative Link on Gastritis Assessment) and OLGIM staging systems use atrophy and intestinal metaplasia extent to stratify gastric cancer risk and guide endoscopic surveillance intervals.
World authority on IBD pathology, dysplasia in Barrett's, and the histological grading of inflammatory bowel disease. Has shaped international consensus criteria for IBD dysplasia reporting over four decades.
Internationally recognised for pancreatic neoplasm classification, NET grading, and ampullary carcinoma pathology. WHO Classification working group contributor for digestive system tumours since the 3rd edition.
World authority on gastric carcinoma molecular classification, hereditary diffuse gastric cancer pathology, and the role of CDH1 germline mutations. Chair of the WHO Classification gastric tumours working group.
UK authority on Barrett's oesophagus dysplasia grading, interobserver variability in Barrett's histology, and the pathological assessment of endoscopic eradication therapy specimens.
Pioneered the classification of serrated colorectal polyps (sessile serrated lesion/adenoma), defined the serrated neoplasia pathway to CRC, and described the CpG island methylator phenotype (CIMP) in colorectal cancer. His work underpins current polyp surveillance guidelines worldwide.
European authority on colorectal cancer staging, extramural vascular invasion (EMVI) reporting, and the ICCR dataset for colon and rectum carcinoma. Editor of multiple ICCR GI pathology reporting datasets.