Table 4

 Histological features in colectomy specimens and their importance

Histological featureDefinitionImportance
CD, Crohn’s disease; LP, lamina propria; IBD, inflammatory bowel disease; IC, indeterminate colitis; UC, ulcerative colitis.
Focal LP inflammationPatchy increase of mononuclear cells in LP separated by areas of normal LP cellularityIn UC can be seen after treatment, may be seen in infection; characteristic of CD especially if intense; may be seen in infection but tends to affect mid and upper crypts and surface epithelium; not helpful in fulminant colitis
Diffuse cryptitisEvenly distributed inflammation of crypts, involving most cryptsCharacteristic of UC, seen in pretreatment material and flares of disease. Avidity of neutrophils for crypts, unlike CD in biopsies and fulminant colectomy specimens
Idiopathic granulomasDiscrete aggregate of macrophages, more than 5 histiocytesAgainst a diagnosis of UC unless crypt related; characteristic of CD, but seen in some infections (TB, yersinia, others); in fulminant colitis against a diagnosis of UC, favours CD
Microgranulomas (small aggregates)A granuloma is defined as 5 histiocytes or more and everything else is not a granuloma, so microgranuloma probably does not existSome believe carries weight in favour of CD
Crypt related granulomas or giant cells/mucin granulomasGiant cells or granulomatous reaction adjacent to a ruptured or injured cryptNo special importance
Muscularis mucosa duplication/hyperplasiaSplaying, thickening, and disorganisation of smooth muscle, sometimes blending with submucosaIndicates previous ulceration; usually seen in CD; may be seen in UC after immunosuppressive treatment for temporisation of severe disease, not helpful in fulminant colitis
Narrow fissuresCleft-like fissure extending into submucosaCharacteristic of CD, but are tracts—usually histiocytes—at periphery and neutrophils centrally (different from fissures seen in IC); may occur in IC and occasionally in UC
Wide fissures, deep undermining ulcers (fig 7A)V shaped clefts that may extend into submucosa or muscularis propria with overhanging edgesTypical for any form of fulminant colitis; typical of all severe IBD and some infections. When undermining ulcers are tangentially cut, they may give the false impression of linear fissures seen in CD (fig 7B)