The forms already described, and especially the epithelioma, occasionally undergo a partial colloid degeneration, but in colloid cancer the cells have a special tendency from the first to undergo colloid metamorphosis, so that even in the more recent parts there is often already a considerable advance in the degeneration. The outlines of the cells disappear as- the protoplasm becomes transformed into colloid material, and as the nuclei resist the degeneration longer, we sometimes see the peculiar appearance of oval nuclei as if floating in a clear transparent material. Finally, the whole epithelial elements are converted into colloid material, and the structure presented is a beautiful reticulated network with spaces tilled with a transparent colourless jelly (Fig. 116, p. 266).
As the colloid material occupies more space than the original cells, the spaces of the alveoli are, as it were, tightly packed with the jelly, and the fibres of the stroma rendered tense and rigid. Hence, although the structure is composed mainly of a soft jelly, yet it is to the feeling hard and rigid, just as a tensely filled bladder may be.
The tumour, like other cancers, usually begins near the pylorus, but it extends gradually till it comes to involve a large area, sometimes even as much as three-fourths of the entire extent of the viscus. The wall of the stomach is converted into a transparent glancing tissue, and in the more advanced parts it is impossible any longer to distinguish the different coats, all being homogeneously replaced by the cancerous tissue. The wall of the stomach is considerably thickened, and the internal surface may present an irregular aspect with prominences; but there is little tendency to ulceration. As the thickened wall is tense and hard, the stomach when cut into does not generally collapse, but keeps its shape. There is no tendency to contraction of the stomach as in scirrhus, but, on the contrary, the organ may be considerably enlarged.
This form has a very marked tendency to extend continuously both along the stomach and also through the stomach to the peritoneum. Hence it produces secondary tumours in the peritoneum itself much more readily than in the lymphatic glands and liver.
The remaining tumours of the stomach are of trivial consequence. We have already seen that Mucous polypi and Cysts occur in chronic catarrh. Lipomas and Myomas have been met with, as also Fibromas and Sarcomas, but they are very rare.
Secondary cancer scarcely ever occurs in the stomach. There may be an extension from the lower end of the oesophagus of Hat-celled epithelioma, and a few cases of metastasis have been observed.
Myoma - Virchow, Geschwiilste, iii., 126. Sarcoma - Wickham Legg, St. Barth. Hosp. Rep., x., 1874; Hardy, Gaz. des. H6p., 1878, p. 25; Virchow, Geschwiilste, ii., 325; Tilger, (with literature) Virch. Arch., cxxxiii., 1893. Cancer - Eokitansky, (Adenoma) Lehrb., iii., 155; Hauser, Magengeschwiir, Bezieh. zur Entwick. des Carcinoma, 1883; Moore, (Cancer in child) Path, trans., xxxvi., 1885; Koster, Die Entwick. der Carcinome; Ebstein, Volkmann's Vortrage, 1875, No. 75; Grawitz, (Metastasis of cancer, and literature) Virch. Arch., lxxxvi., 1881; Coupland, Path, trans., xxvii., 1876, p. 264; Perry and Shaw, Guy's Hosp. Reports, xlviii., 1891.