Jass J R, Strudley I, Faludy J
Scand J Gastroenterol Suppl. 1984;104:109-30.
Histochemical techniques reveal the functional divergence of carcinomas of the gastrointestinal tract and their tissues of origin. The principal changes are either the impairment or loss of normal functions or the acquisition of new functions. The latter may be those of heterologous adult tissues (metaplasia) or foetal tissues. Dysplasia or intra-epithelial neoplasia is regarded as a selective precancerous lesion. One might predict the functional profiles of dysplasia to be intermediate between those of normal and carcinomatous tissues. This appears to be only partially true in that high grade dysplasia (amounting to carcinoma-in-situ) will show appropriate cancer-associated changes, whereas low grade dysplasia may be functionally identical to its normal counterpart. Paradoxically, it is possible to demonstrate cancer-associated changes in non-neoplastic lesions such as incomplete intestinal metaplasia of gastric mucosa and both metaplastic polyps and transitional mucosa of the colorectum. If a proportion of the changes occurring in the course of malignant transformation have a metaplastic basis, it is possible that these are caused by the same environmental agents which lead to benign metaplasias. Benign metaplastic lesions may signal the presence of a potentially carcinogenic microenvironment, whilst some, such as incomplete intestinal metaplasia, are regarded as precancerous.
组织化学技术揭示了胃肠道癌及其起源组织的功能差异。主要变化要么是正常功能的损害或丧失，要么是获得新功能。后者可能是异源性成人组织（化生）或胎儿组织的功能。发育异常或上皮内瘤变被视为一种选择性癌前病变。有人可能预测发育异常的功能特征介于正常组织和癌组织之间。这似乎只是部分正确，因为高级别发育异常（相当于原位癌）会显示出与癌症相关的适当变化，而低级别发育异常在功能上可能与其正常对应物相同。矛盾的是，在非肿瘤性病变中，如胃黏膜不完全肠化生、结肠直肠化生息肉和移行黏膜，也可能显示出与癌症相关的变化。如果恶性转化过程中发生的一部分变化有化生基础，那么这些变化可能是由导致良性化生的相同环境因素引起的。良性化生病变可能预示着潜在致癌微环境的存在，而一些病变，如不完全肠化生，被视为癌前病变。
