Epithelioma is a malignant new growth having its origin in the epithelial cells of the skin or mucous membrane. It is a disease of middle and old age, being somewhat rare before 30 and most common after 50. There is no sharp line of demarcation between the superficial and the deep, nodular or tubercular form of epithelioma. The latter often begins as a firm nodule which in its development extends deeply into the skin and projects well above the surface. The lower lip is the seat of nearly one-half of all epitheliomas, and in this location the growth is almost always of the deep variety. It often occurs because of the irritation produced by smoking.
In the course of months or years the tumor may reach the size of a cherry or walnut; occasionally with greater lateral spread it assumes the shape of a thick plaque one inch or more in diameter. The new growth is very firm and its covering is usually delicately vascularized and pink or yellowish, with a semi-translucent appearance. In the neighborhood may be one or more smaller nodules. Sooner or later degeneration occurs at the middle of the growth and an ulcer is formed, characterized by its prominent, roll-like waxy border, its steep edges and the frequently glazed appearance of its granulation tissue, which, however, may be moist or crusted. Even before ulceration the tumor may cause shooting pains by the compression of small nerve filaments.