The neoplasms which belong to this group originate in the epithelial and glandular structures of the organ, and have been variously described at different times. By the earlier writers they were classified according to their general features as hard and soft cancers, villous and fungoid growths, or cancerous ulcers; while at a somewhat later date certain special varieties were recognised by the terms'scirrhus,' 'encephaloid,' ' villous,' and ' colloid.' This nomenclature, while it expresses more or less succinctly the naked-eye appearances of the principal forms of the disease, affords but little clue to their morphology, and it has therefore become necessary to classify them according to their histological structure. By means of the microscope three types of primary cancer of the stomach may be recognised. In the first of these the cellular elements are similar in shape and size to the cells which normally line the gastric tubules, and it has consequently received the name of 'glandular' or ' spheroidal-cell; carcinoma. Inasmuch, however, as both the macroscopic and microscopic features of the growth vary according to the amount of fibrous tissue it contains, it is convenient to distinguish a hard variety (scirrhus) from a soft form (medullary). In the second type the tubular and hollow spaces in the matrix are lined by columnar cells like those which exist in the pyloric glands, and to this the term ' cylindrical-celled carcinoma : or ' adenocarcinoma ' is applied. Lastly, each variety may undergo myxomatous degeneration, which affects both the cells and fibrous stroma, and transforms the tumour either wholly or in part into a firm gelatinous mass termed ' colloid carcinoma.'
These different varieties are not always sharply distinguished from each other, but are apt to present many gradations and transitional forms. Thus, a soft spheroidal-celled growth may possess a hard fibrous base, or a typical scirrhus may be covered with fungoid outgrowths ; while in rarer cases the neoplasm may exhibit a cylindrical-cell formation at one spot and a spheroidal-cell structure at another.
(Soft (Medullary or Encephaloid).