Primary cancer oŁ the stomach may be of the cylindrical or spheroidal, very rarely of the squamous type (Rolleston, Journ. Pathology and Bacteriology, August, 1905).
If the stroma be abundant the term " scirrhus or hard cancer" is applied, and if the stroma be scant}r the cancer is spoken of as " medullary " ; moreover, either may take on a colloid form.
Fenwick, out of 115 cases, found 63.3 per cent, of the spheroidal type, 28.6 per cent, of the cylindrical type and 7.8 per cent, in which the growth was undergoing colloid degeneration.
Of 41 cases of spheroidal-celled carcinomata 22 were of the soft or medullary and 19 of the scirrhous variety.
Such differences in classification and relative percentages in each class are found in writings on this subject that statistics as to relative frequencies of the different varieties would seem to have little value; moreover, there are so many tumours occupying intermediate positions between the various classes that accurate classification is really difficult.
With regard to ulceration, metastasis and secondary growths, there is no striking difference between the two chief varieties of the disease.
Secondary carcinoma of the stomach is not very common and is unimportant from a clinical standpoint, as surgical treatment is contra-indicated in all such cases. Welch collected 37 cases of which 17 were secondary to mammary cancer, 8 to cancer of the oesophagus, 3 to cancer of the mouth and nose, and 9 to cancer in other parts of the body.
An analysis of 1796 cases compiled from various authors showed the pylorus to be affected in 1110, the lesser curvature in 197, the cardiac orifice in 158, and the rest of the stomach in 331 (Furnival).
Dissemination of cancer usually occurs through the lymphatics, but growth in cancer of the stomach may be disseminated by the blood-vessels, especially the portal vein. Extension may also occur through adhesions or by direct implantation on a neighbouring surface through contact.