The functions of epithelial tissues are to protect, excrete, and absorb. Cancer originating in the epithelial tissue is called a carcinoma. Connective tissue consists of elastic, fibrous, and collagenous tissues, such as bone, cartilage, and fat. The function of such tissue is to connect, support, and protect. Cancers originating in connective tissue and in muscle are called sarcomas.
Nerve tissue includes the brain, spinal cord, and nerves.
Tumors arising in nerve tissue do not have a common name, but are named specifically for the type of cell involved. For example, tumors arising from astrocytes, a type of glial cell thought to form the blood-brain barrier, are called astrocytomas. Tumors arising in nerve tissue are often benign, but, because of their critical location, are more likely to be harmful than benign tumors in other sites. Below is a list of benign and malignant tumors according to their tissue of origin. A tumor's histologic type is determined by the appearance and organization of the cells when examined under a microscope.