Definitions of some histological features
| Feature | Figures | Definition/description | Additional comments | References |
|---|---|---|---|---|
| Villiform/irregular mucosal surface | 2D | Undulating or broadly villiform surface. Wide crypt mouths | Separation of crypts yielding surface contour of broad villus-like projections | 3 4 |
| Crypt distortion | 2D–F | May include branching, loss of parallelism, irregularity, tortuosity, dilatation and variation in shape and size | Caution adjacent to crypt abscesses and lymphoid aggregates/follicles. Anal transition zone/columnar cuff unsuitable for assessment | 3 18 19 25 28 31–33 |
| Crypt branching | 2E,F | Two or more branched crypts in a well-oriented biopsy. Included in crypt distortion | Branching between mucosal hillocks/at innominate grooves is normal | 11 18 19 25 28 34 |
| Crypt atrophy | 2D | Minimum: crypt shortening, with increased gap between crypt base and muscularis mucosae. Additional evidence: wider spacing of crypts; >1 crypt diameter between crypts | Caution near lymphoid follicles and near muciphages. Anal transition zone/columnar cuff unsuitable for assessment. Intercrypt/subcryptal spaces may be higher in caecum and rectum | 1 3 11 18 21 25 28 33 |
| Basal plasmacytosis | 2G | Plasma cells at base of mucosa. May separate crypts from muscularis mucosae but not always subcryptal. Loss of plasma cell gradient | Basal plasma cells are normal in the caecum and ascending colon | 3 4 18 28 |
| Basal lymphoid aggregates | 2H | Nodular collections of lymphocytes with or without germinal centres. May be between muscularis mucosae and crypts | One or two transmucosal lymphoid nodules can be seen in normal mucosa; can extend across muscularis mucosae. Pathological aggregate may be difficult to distinguish from normal | 3 18 19 25 |
| Cryptitis | Neutrophils in crypt epithelium | 18 28 31 | ||
| Crypt abscess | Neutrophils in crypt lumen | Often located near base of crypt | 18 28 31 34 | |
| Granulomas | 3A | Discrete collection of at least five epithelioid macrophages | Consider crypt rupture as a cause. Serial sections may help with this | 11 18 25 |
| Mucin depletion | 2D,F | Unequivocal reduction of goblet cell mucin in crypt epithelium | Mucin in normal mucosa may be reduced near lymphoid follicles. Depletion can reflect bowel preparation | 11 19 21 35 |
| Paneth cell metaplasia | 3B | Pyramidal crypt epithelial cells with supranuclear eosinophilic granular cytoplasm | Normal in caecum and right colon, probably as far as splenic flexure | 19 25 |