Prognostic significance of type IV collagen and laminin immunoreactivity in urothelial carcinomas of the bladder. Invasion of a carcinoma involves the degradation and penetration of the subepithelial basement membrane (BM). This phenomenon might be used for histopathologic evaluation of neoplasms of the bladder. The authors studied the clinicopathologic data and tissue specimens of 125 cases of urothelial carcinomas collected prospectively. Penetration of the BM was evaluated by immunohistochemical staining of the BM components laminin and type IV collagen. The use of this parameter as a prognostic indicator in bladder cancer was assessed. The 5-year survival rate of patients having tumors with an interrupted or absent BM was significantly lower than that of patients having tumors with an intact BM. The rate of progression was greater in tumors with an interrupted or absent BM than in tumors with an intact BM. No association was found between BM status and recurrence. However, a significant correlation between tumor stage and BM staining was found. A correlation was also found between ploidy and BM staining as well as between histologic grade and BM staining pattern. When evaluating histologic grade, stage, ploidy, age, and BM score as prognostic parameters, the stage of bladder carcinomas turned out to be the most important factor in predicting the survival rate and the progression-free survival. However, BM staining was found to be of value for early identification of microinvasion and is helpful for correct staging of urothelial carcinomas. 