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Often called a mole or beauty mark, a compound nevus is a cluster of cells found in both the upper layer of skin, called the epidermis, and the underlying dermis. It is usually hereditary and more typically appears in children and young adults. Research also suggests that ultraviolet light from the sun can cause nevus cells and other benign neoplasms, or non-cancerous growths of cells, to develop. A compound nevus typically has a higher concentration of pigment called melanin, and is therefore usually darker than the rest of the skin. People with a lot of these moles are sometimes at a higher risk for developing melanoma, a type of skin cancer.
A compound nevus can consist of three different types of cells. Epithelioid, or Type A, cells are usually found in the top layer of skin as well as the upper part of the dermis. These typically produce melanin and contain a substantial amount of fluid in the cell called cytoplasm. Generally deeper are lymphocytoid, or Type B cells, in the dermis that look similar to immune cells called lymphocytes under a microscope. The deepest layer of compound nevus cells are classified as type C, which are typically elongated and situated within fibrous tissue.
Dark hair can sometimes grow out from a compound nevus, which can be removed in various ways. If someone tries to remove a mole without medical help, it can cause irritation and scarring. Sometimes a physician uses a laser to remove the abnormality if necessary, but surgeons can also freeze the area and cut it away with a scalpel if it extends deeper into the skin. Compound nevus treatment is usually necessary only if one is bothered by the mole, or if it changes in size, shape, or color. Bleeding, itching, and inflammation can also be signs for concern, as well as if the borders become irregular or ragged.
Variations of skin marks, similar to a compound nevus, include the junctional nevus, a brown or black cluster of cells that sit in between the two layers of skin. An intradermal nevus is typically located in the lower layer of skin, and is often raised and not different in color from the surrounding area. There are many abnormalities of skin cells that can look suspicious, yet a medical professional can often tell them apart from more serious problems. Sometimes a biopsy is performed to test the skin sample in a laboratory to determine the exact nature of the cells.