The _columnar epithelial cancer_ or _columnar epithelioma_ originates in mucous membranes covered with columnar epithelium, and is chiefly met with in the stomach and intestine. As it resembles an adenoma in structure it is sometimes described as a _malignant adenoma_. Its malignancy is shown by the proliferating epithelium invading the other coats of the stomach or intestine, and by the development of secondary growths. _Glandular carcinoma_ originates in organs such as the breast, and in the glands of mucous membranes and skin. The epithelial cells are not arranged on any definite plan, but are closely packed in irregularly shaped alveoli. If the alveoli are large and the intervening stroma is scanty and delicate, the tumour is soft and brain-like, and is described as a _medullary_ or _encephaloid cancer_. If the alveoli are small and the intervening stroma is abundant and composed of dense fibrous tissue, the tumour is hard, and is known as a _scirrhous cancer_--a form which is most frequently met with in the breast. If the cells undergo degeneration and absorption and the stroma contracts, the tumour becomes still harder, and tends to shrink and to draw in the surrounding parts, leading, in the breast, to retraction of the nipple and overlying skin, and in the stomach and colon to narrowing of the lumen. When the cells of the tumour undergo colloid degeneration, a _colloid cancer_ results; if the degeneration is complete, as may occur in the breast, the malignancy is thereby greatly diminished; if only partial, as is more common in rectal cancer, the malignancy is not appreciably affected. Melanin pigment is formed in relation to the cells and stroma of certain epithelial tumours, giving rise to _melanotic cancer_, one of the most malignant of all new growths. Cyst-like spaces may form in the tumour by the accumulation of the secretion of the epithelial cells, or as a result of their degeneration--_cystic carcinoma_. This is met with chiefly in the breast and ovary, and the tumour resembles the cystic adenoma, but it tends to infect its surroundings and gives rise to secondary growths. _Rodent cancer_ originates in the glands of the skin, and presents a special tendency to break down and ulcerate on the surface (Figs. 102 and 103). It almost never infects the lymph glands. DERMOIDS A dermoid is a tumour containing skin or mucous membrane, occurring in a situation where these tissues are not met under normal conditions.