Colloid Or Alveolar Cancer is a tumour characterized by the occurrence of colloid degeneration of epithelial cells. It is met with chiefly in the stomach and intestines, and in the mamma; more rarely elsewhere.
There is here a definite new-formation both of stroma and epithelial masses, and the stroma is often produced in the most beautiful and characteristic forms (see Fig. 116). As if it were in the plan of the growth, the cells regularly undergo colloid degeneration, and finally the masses of cells become converted into masses of colloid material which fill the spaces. In the bulk of the tumour therefore there may be nothing visible beyond the regularly formed stroma whose spaces are filled with clear transparent material. Occasionally there may be in the centres of the alveoli some remains of the cells visible, while the peripheral cells are already completely converted.
Fig. 110. - Colloid cancer. A finely reticulated stroma is seen with meshes full of colloid material, the cells having disappeared, x 90.
To the naked eye such tumours have a markedly gelatinous appearance, and as the fibrous stroma may in its coarser meshes be visible without the microscope, it may, even to the naked eye, look as if there were nothing but alveoli filled with gelatinous material, hence the name alveolar cancer. The tissue is frequently densa and hard to the feel. This arises from the fact that the alveoli are tensely packed with the colloid material, and, the fibres being on the stretch, a dense resistance is offered, just as a tightly blown up bladder is hard.
These tumours mostly occur as infiltrations, frequently penetrating among the constituents of the tissues, and although they very often extend widely by continuity (as in the stomach), they show little tendency to metastasis; even when they attack the lymphatic glands secondarily they do not usually produce large tumours.