[Tenascin: a simple tool in the diagnosis of collagenous colitis]

Collagenous colitis is characterised clinically by chronic, voluminous, watery diarrhoea, and histopathologically by a thickened subepithelial collagen layer and infiltration of the lamina propria with inflammatory cells. In practice, the exact measurement of this subepithelial collagen layer is complicated by its blunt limit, a nonorthogradely affected cell layer and often only focal findings. Immunohistochemically, the subepithelial collagen layer stains positively with the glycoprotein tenascin, a marker for extracellular matrix remodeling.

To assess if immunohistochemical staining with tenascin could be used as a simple and practical tool in the diagnosis of collagenous colitis.

86 of the routinely examined colon biopsy specimens with the following initial diagnosis: 33 collagenous colitis, 21 lymphocytic colitis, 15 inflammatory bowel disease (ulcerative colitis or Crohn's disease), 8 unspecific inflammation and 9 without histopathological findings, were incubated with tenascin. They were then evaluated blindly by 5 different investigators (2 senior pathologists, 2 assistant doctors and 1 chief assistant of the laboratory experienced in immunohistochemistry). Each specimen was evaluated semiquantitatively from 0 (for no tenascin-positive subepithelial collagen layer) to 3 (wide, clearly tenascin-positive collagen layer).

In specimens with the initial diagnosis "collagenous colitis" the semiquantitatively assessed subepithelial collagen layer was significantly wider than in specimens with other initial diagnosis. Experience and educational level of the investigators did not influence the results.

Immunohistochemical incubation with tenascin is a simple, economical and rapid tool in the diagnosis of collagenous colitis. With the aid of tenascin staining collagenous colitis can be differentiated histopathologically with sufficient accuracy from other colitis.