Comparative studies of primary, metastatic and transplanted colon adenocarcinomas of Fischer 344 rats.

Morphological and histochemical characteristics of two sets of metastatic and transplanted adenocarcinomas were compared to those of the parent primary colon carcinomas induced by azoxymethane (8 mg/kg/week) in Fischer 344 rats. The histochemical features of the primary carcinomas and their respective metastatic and transplanted carcinomas were similar; however, there were marked morphological differences between these lesions. The primary adenocarcinomas were both well-differentiated glandular and mucinous colloid in type. Histochemically, both the types showed marked diminution of sulfomucin and increased sialomucin in the primary lesions as well as in the secondary sites. By light microscopy, the general histological pattern of the primary carcinoma was maintained by the secondary lesions. Compared to normal colon epithelia, the primary carcinoma showed mildly increased exfoliation of cells, and the transplanted carcinomas demonstrated profound exfoliation of epithelial cells in the glandular lumen, whereas the metastatic carcinomas showed moderate exfoliation. The three basic cell types of colon (undifferentiated cells, mucous cells and endocrine cells) were seen in variable proportions in the primary and secondary lesions with inconsistent pattern of cellular differentiation in the secondary lesions of the same primary. In the liver, intercellular junctions were seen between the metastatic carcinoma cells and the host hepatocytes indicating establishment of physical and probably biological communication between the metastatic cancer cells and the host cells.