A carotid body tumor, also known as a chemodectoma or paraganglioma, is a tumor located on the side of the neck, where the large carotid artery branches into smaller blood vessels to carry blood into the brain. The cluster of cells around that branching is called the carotid body, or carotid glomus. A tumor may be a mass or lump of tissue which will resemble swelling. Not all tumors are cancerous, but it's an honest idea to ascertain a doctor if one appears. In a healthy body, cells grow, divide, and replace one another within the body. As new cells form, the old ones die. When an individual has cancer, new cells form when the body doesn't need them. If there are too many new cells, a gaggle of cells, or tumor, can develop.