The value of immunohistochemistry for collagen IV expression in colorectal carcinomas. The Dukes' classification has well-established prognostic value in colorectal cancer patients. Yet, in each Dukes' class, the survival of individual patients may vary considerably. Recent studies show prognostic significance of genetic alterations in colorectal carcinoma. However, the importance of tumor stromal components noted in the surrounding tissue may have been overlooked by the methods used. Therefore, in a longitudinal study of 154 patients with colorectal cancer operated on between 1967 and 1974, the authors determined the influence on prognosis of lymphocytic infiltration and expression of collagen type IV in tumor stroma. Also, age, sex, Dukes' classification, grade of tumor differentiation, vasoinvasion, and the number of positive lymph nodes were analyzed. Follow-up was at least 15 years. Lymphocytic infiltration and collagen IV expression were scored as mild, moderate, or severe. Survival was analyzed by a Cox proportional-hazards model. The density of lymphocytic invasion showed no significant influence on survival. Collagen IV expression analyzed as a single variable was significantly (P = 0.038) related to better prognosis in colorectal cancer patients. By multi-variate analysis collagen IV expression showed a trend toward better prognosis that was not statistically significant (P = 0.12). Dukes' classification (P less than 0.001), the presence of vasoinvasion (P = 0.009), and lymph node status (P = 0.04) significantly influenced survival. In conclusion immunohistochemistry for collagen IV is an important additional staining technique with prognostic value. In addition, collagen IV immunostaining facilitates recognition of vascular invasion by highlighting the basement membrane of vessels. 