Words to know: These definitions may help as you discuss your diagnosis and treatment with your health care team.

Cutaneous: Related to the skin.

Dermatologist: A doctor trained in dermatology, a medical field dealing with skin function and diseases.

Dermis: The middle layer of the three main layers of the skin. The dermis has connective tissue, blood vessels, sebaceous (oil) and sweat glands, nerve endings, hair follicles and other structures.

Epidermis: The visible part of your skin; the thin, outermost layer that acts as a barrier to protect the body against infection, injury and the sun’s ultraviolet (UV) rays.

Hypodermis: The innermost of the three main layers of the skin, sometimes called subcutaneous tissue. It consists of fat, lymphatic vessels and connective tissue.

In-transit metastasis: A type of metastasis in which skin cancer spreads from the primary tumor through a lymphatic vessel and begins to grow in the lymphatic vessel before it has reached the nearest lymph node.

Lymphocyte: A type of immune cell (white blood cell) in lymph tissue and blood that helps the immune system fight infections and cancer. The main types are B-lymphocytes (B-cells) and T-lymphocytes (T-cells).

Microsatellite tumor: A tumor that can be seen only with a microscope.

Pigment: A substance that gives color. In the body, the pigment melanin gives color to the skin, eyes and hair.

Progression-free survival: The length of time during and after treatment that a patient lives with the disease but it does not get worse.

Satellite tumor: A group of tumor cells in an area near the primary (original) tumor. In melanoma, satellite tumors occur close to the primary tumor (within 2 centimeters), on or under the skin, and can be seen without a microscope. Microsatellite tumors, on the other hand, can be seen only with a microscope.

Sun protection factor (SPF): A rating scale for sunscreen products indicating how long a particular product provides protection against sunburn. The higher the SPF number, the longer the protection.

Topical: Refers to medication applied to a surface of the body, such as the skin or mucous membranes, usually as an ointment, cream, gel, etc.

Tumor microenvironment: The area that surrounds and sustains a tumor. It is made up of tumor cells, normal cells, immune cells and blood vessels.

Ultraviolet (UV) radiation: Invisible rays from the sun that can cause sunburn, premature aging of the skin, melanoma and other skin cancers, and eye problems. UV radiation also comes from tanning beds and sun lamps.

Some definitions courtesy of the website of the National Cancer Institute (