EPITHELIOMA

a cancerous growth or tumour consisting of tissue derived from the skin or mucous membrane (epithelium)a type of carcinoma (q.v.). Various types of epitheliomas occur, related to the different types of epithelial cells that exist, such as basal cell epitheliomas, involving the inner layers of the skin, and squamous cell epitheliomas, involving the scalelike outer cells of the skin. Epitheliomas are usually benign, and though they may spread into adjoining tissues, only rarely do they metastasize; i.e., send cancerous cells through the body cavities, bloodstream, or lymphatic system.