Tumour basement membrane laminin in adenocarcinoma of rectum: An immunohistochemical study of biological and clinical significance

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Abstract
Well‐defined basement membrane laminin was seen in 98/158 (62%) rectal adenocarcinomas stained by an immunoperoxidase method. Only 27 (28%) patients with laminin‐positive tumours developed distant metastases, compared with 39 (65%) patients with laminin‐negative carcinomas. The corrected 5‐year survival rates for patients with laminin‐positive and laminin‐negative tumours were 65% and 23%, respectively. Twenty‐five out of 30 (83%) well‐differentiated adenocarcinomas and only 3/15 (17%) poorly differentiated tumours contained basement membrane laminin, with moderately differentiated carcinomas showing intermediate laminin status (70/110, 64%, laminin positive). Forty‐three of 60 (72%) of laminin‐negative tumours had metastasized to regional lymph nodes. These data suggest that laminin may be a marker for differentiation. However, laminin status yields information about tumour behaviour which is not confined to stage and grade, and multivariate analysis shows that it is a better indicator of prognosis than tumour grade as assessed by conventional histology. Although laminin status alone is a less useful predictor of prognosis than Dukes' stage, a patient with a laminin‐positive adenocarcinoma of rectum is 2.7 times as likely to survive 5 years than a patient with a laminin‐negative tumour. Assessment of laminin status, together with Dukes' stage is, therefore, commended as a more precise and objective indicator of prognosis than histological degree of differentiation in colorectal carcinoma.