Basement membranes in urothelial carcinoma

Invasion of a bladder tumour involves the degradation and penetration of the subepithelial basement membrane. A retrospective study of 69 superficial and 15 invasive transitional cell carcinomas of bladder and a prospective study of 43 mucosal biopsies were performed in order to assess the usefulness of immunohistochemical staining of the basement membrane components, type IV collagen and laminin as prognostic indicators in superficial bladder cancer. There was a significant association between pT category and basement membrane staining. The incidence of progression of superficial tumours with patchy or absent basement membranes was significantly greater than those with complete basement membranes but there was no association with superficial recurrence. Biopsies of dysplastic epithelium had thickened and reduplicated basement membranes, possibly as a result of increased cell turnover. The results suggest that a balance exists between basement membrane production and degradation in early malignancy. This technique may be of value in the early identification of microinvasion and in the prediction of subsequent progression.