Immunohistochemical observations of keratins, involucrin, and epithelial membrane antigen in urinary bladder carcinomas from patients infected with Schistosoma haematobium.

Squamous cell carcinomas of the urinary bladder and the epithelial lesions associated with infection by Schistosoma haematobium were histopathologically and immunohistochemically described for keratin proteins (TK, 41-65 kDa; KL1, 55-57 kDa; PKK1, 40, 45 and 52.5 kDa), involucrin, and epithelial membrane antigen (EMA). Normal urothelial epithelium was positive for all keratins, and showed absent or slight reactions for involucrin and EMA in superficial umbrella cells. The intestinal type of epithelium was composed of columnar cells and small basal cells; TK was positive in the basal cells, KL1 staining was positive in the columnar cells, whereas PKK1 was negative or slight in the columnar cells. Involucrin was confined to columnar cells. Squamous metaplastic epithelium showed a rather regional keratin distribution: TK was distributed in all layers, KL1 decorated upper spinous and granular layers, but PKK1 did not bind, and involucrin staining existed only in upper spinous and granular cells. Keratin expression in squamous cell carcinomas indicated heterogeneity and its stainability was dependent on the degree of keratinization: The G 1 type revealed strong reaction, the G 2 type showed a similar distribution pattern, but the staining intensity was less, and the G3 type showed irregular staining with decreased intensity. Involucrin staining was limited to keratinized cells of carcinoma as was that for EMA.