Glossary of Dermatology Terms

Take advantage of our dermatology glossary to help get a better understanding of your skin and skin risks.B C D E F G H I J K L M N O P Q R S T U V W X Y
Actinic >keratosis
(pl. keratoses): A lesion that may form on skin exposed to the ultraviolet (UV) rays of the sunlight for many years. The lesion can progress to squamous cell carcinoma, a type of skin cancer that can spread.
ABCDs of melanoma detection: ABCD is an acronym used to help people remember the key characteristics of melanoma detection — asymmetry (A), border irregularity (B), and color within varies (C). The “D” stands for diameter. While melanomas are usually greater than 6 millimeters (size of a pencil eraser) when diagnosed, they can be smaller. If you notice a mole different from others, or which changes, itches, or bleeds even if it is smaller than 6 millimeters, you should see a dermatologist.Adjuvant therapy: Any treatment given after the first that is intended to increase the effectiveness
of the first treatment.Atypical mole: See dysplastic.BCG:
Bacille Calmette-Guérin (BCG) is a vaccine made from a form of killed tuberculosis that is used to immunize people against tuberculosis (TB). This vaccine is being investigated as a possible treatment for advanced melanoma.Biopsy: Removal and microscopic examination of tissue from the body for the purpose of establishing a precise diagnosis. A biopsy is required to confirm a skin cancer diagnosis. During an excisional biopsy, the entire skin lesion is removed for microscopic examination. When an incisional biopsy is performed, a portion of the skin lesion is removed.

Basal cell carcinoma: A type of skin cancer that arises in the basal cells, which are located in the epidermis (outermost layers of the skin). It can take many forms and accounts for about 80% of all skin cancers. Basal cell carcinoma can be locally invasive, but rarely metastasizes.

Benign:Not malignant.

Blinded:Term used in an investigational study, such as a clinical trial, that means none of the volunteers know if they are receiving the investigational treatment, standard treatment, or a placebo (if a placebo is used). When both the volunteers and researchers do not know who is receiving which treatment, the study is said to be “double blinded.”

Chemotherapy: Use of anti-cancer medications to kill cancer cells that survive surgery or cannot be reached by surgery. Chemotherapy also may be used in the late stages to reduce symptoms or the size of a tumor.

Clark level of invasion: Classification system developed by dermatopathologist, Wallace Clark, MD, that indicates how deeply a primary melanoma tumor has penetrated the skin. Five levels are used. Level I, also called “melanoma in situ” indicates that the melanoma is confined to the epidermis, the outermost layer of the skin. Levels II – IV indicate that the tumor has invaded the dermis, the middle layer of the skin, and each of these levels corresponds to a different depth. When a melanoma is classified as a Level V, it has invaded the subcutis, the fatty layer under the skin.

Clinical trial: A medical investigational study in which humans are observed and/or treated. A study may investigate a new treatment, prevention strategy, diagnostic method, screening procedure, or how to improve comfort and quality of life.

Control: In an investigational study such as a clinical trial, this is the group that receives the standard treatment, no treatment, or a placebo rather than the treatment being studied.

CT scan: Computed tomography (CT), which is sometimes called a CAT scan, combines x-ray and computer technology to produce cross-sectional images of the body. Unlike an x-ray, which images bones, computed tomography can produce an image that shows everything in that area of the body, such as organs, bones, and blood vessels. These images can help detect cancer that has spread to an organ
or a lymph node.

Cytokines: Proteins produced naturally in the body that act as “messengers” to initiate inflammatory and disease-fighting responses to viruses, bacteria, toxins, injury, and malignant processes. Cytokines are in use as anti-cancer medications.

Dermatopathologist: A medical doctor trained in both dermatology and pathology who uses this expertise to microscopically examine tissue in order to diagnose skin conditions, often providing expertise in diagnosing difficult cases.

Dermatoscopy: Also called “surface microscopy,” “dermoscopy,” and “epiluminescence microscopy,” this is a noninvasive technique used by dermatologists to examine pigmented and some non-pigmented lesions. The technique involves using a handheld microscope-like device that allows the dermatologist to see through the stratum corneum (bottom of the outermost layer of skin), permitting a detailed view of structures within the skin that are usually invisible to the unaided eye. Dermatoscopy can aid in early detection, help determine which skin lesions should be biopsied, and assist surgeons in determining how much normal-looking skin to remove.

Dermis: The middle layers of skin, which consists largely of collagen and elastin and supports the upper layers known as the epidermis.

Distant: Cancer has spread from the original tumor and beyond the lymph nodes closest to the original tumor to other lymph nodes and/or organs.

Distant site: Once skin cancer spreads beyond the  lymph nodes nearest the original (primary) tumor, it has traveled to a “distant site.” A distant site may be an internal organ, skin not near the primary tumor, or lymph nodes other than those closest to the primary tumor.

Dysplastic: An alteration in size, shape, and organization of cells. A dysplastic nevus, also called an “atypical mole,” is characterized by the ABCDs of melanoma detection.

Epidermis: Outermost layers of skin.

Fine needle aspiration biopsy: Also called FNA, this type of biopsy is performed by inserting a long, thin needle in order to extract a small amount of tissue. The tissue is examined under a microscope to find out if cancer cells are present. This type of biopsy may be used to collect cells from an enlarged lymph node or an internal organ, such as the liver or a lung.

Immunotherapy: Treatment that repairs, stimulates, or enhances the body’s own immune responses to fight established disease. It is sometimes combined with chemotherapy.

In situ: Skin cancer exists in the outermost layer of skin only and is said to be in stage 0. The term “in situ” literally means “in the original position or place.”

Informed consent: When a person agrees to volunteer for a clinical trial, the person agrees in writing that he or she has been informed about what will occur during the study, the risks and benefits, whether or not the study will be blinded, and other key information. A volunteer can withdraw at any time; however, it is hoped that every volunteer will stay for the duration of the clinical trial.

Interferon: Interferons are substances within the immune system that are produced in response to infection. One type, interferon-alpha, is FDA-approved for treating melanoma in certain stages when used along with another therapy, such as surgery. In these stages, interferon-alpha injections can help prevent recurrence and increase the likelihood that all cancer is eliminated.

Interleukin: Interleukins activate the “killer” activities of specific white blood cells in the immune system. One specific interleukin, IL-2, helps the immune cells reproduce more quickly and is used to treat melanoma that has spread.

Intravenous: Within a vein or administered directly to a vein. Some medications, such as dacarbazine (DTIC) which is used to treat advanced melanoma, are administered this way.

Lentigo maligna: The in situ form of lentigo maligna melanoma.

Lentigo maligna melanoma: See melanoma.

Lymph node: Part of the immune system, lymph nodes are small bean-shaped glands found throughoutthe body. The glands trap bacteria, viruses, and other foreign substances, such as cancer cells. Lymphocytes, a type of white blood cell, work to destroy the foreign substances. Clusters of lymph nodes can be felt in the neck, groin, and under the arms. In these areas, the lymph nodes can swell noticeably when fighting foreign substances.

Malignant: When referring to cancer, the ability to grow and spread in an uncontrolled manner beyond the
local confines of the tumor.

MarginRefers to the amount of normal-appearing tissue to be removed along with the tumor during surgical excision. The thicker the tumor, the more normal-looking skin the surgeon removes. Margin is usually measured in centimeters. Current recommended surgical margins for melanoma are:

Tumor Thickness (millimeters)

In situ melanoma

less than 1.0

1.0 – 4.0

more than 4.0

Excisional Margin (centimeters)




at least 2.0

Surgical margins may be modified for an individual patient after considering medical or esthetic reasons.
The main goal is complete removal of the cancer.

For an explanation of the relationship between tumor thickness and 5-year survival rate, see thickness.

Melanocytes: Cells that make melanin, the substance that gives skin its color. Melanin is made in small granules, called melanosomes, within the melanocyte. Melanin is then transported to cells in the outer skin
(keratinocytes), where the melanin is seen as the “color” of the skin.

Melanoma: A cancerous tumor that arises in the melanocytes and accounts for about 4% of all skin cancers.
Four types of melanoma are most common:

Acral lentiginous melanoma (ALM): The most common melanoma in dark-skinned people, it appears on
palms, fingers, toes, soles, mucous membranes, and underneath fingernails and toenails. This tumor accounts for 2% of melanomas in Caucasians and 50% in dark-skinned races. As the tumor is frequently mistaken for a bruise or nail streak in its early stages, ALM is often not diagnosed until the later stages when the tumor is very aggressive.


Lentigo maligna melanoma (LMM): Melanoma that develops in a sun-induced freckle. It typically occurs
on sun-damaged skin in the elderly and may be mistaken in its early, and most treatable, stages for a benign “age spot” or “sun spot.” It accounts for about 10% of melanomas diagnosed in the United States. Since LMM is so
easily mistaken as a benign patch of mottled skin, it can go undetected for years. This can be quite


Nodular melanoma: A very aggressive form of melanoma that tends to grow “down” into deeper skin tissue rather than along the surface of the skin. It accounts for approximately 15% of diagnosed melanomas.


spreading melanoma
: This is the most common type of melanoma, which accounts for about 70% of all diagnosed melanomas. This melanoma usually spreads along the skin’s surface (epidermis) and then grows “down” into deeper skin tissue (dermis). It is curable when it is removed before it invades the dermis.

Less common types of melanoma include:

Amelanotic melanoma: When this type of melanoma occurs, not enough pigment is produced to create a dark-colored lesion. Instead, the lesion may be skin-colored or slightly reddish like an insect bite. It usually
appears as a pink or red nodule.

Desmoplastic neurotrophic melanoma: This usually looks like a non-pigmented scar-like lesion. It is suspected if a lesion, such as a scar or keloid, is found and persists at a site when no injury occurred to cause the lesion. The tumor may be pigmented or non-pigmented and most commonly appears on sun-damaged skin of the head and neck in elderly adults.

Mucosal melanoma: This melanoma occurs in mucosal regions of the mouth, nose, and genitals. It may not be recognized because it occurs in sites that are infrequently examined.

Metastasis: The spreading of disease from one part of the body to another. Both melanoma and squamous cell carcinoma metastasize. Melanoma most often spreads to the lymph nodes, liver, abdomen, lungs, bone, skin, heart, and brain.

Mohs surgery: A highly specialized surgical technique in which all remaining visible parts of the tumor
are excised and skin is removed layer by layer and examined under a microscope while the patient is undergoing surgery. Skin continues to be removed until cancer is no longer detected. Not necessary for removing all skin cancers, it may be used when the primary tumor is located on the face or another area where it is essential to preserve as much healthy tissue as possible, the tumor is large, it is difficult to determine where the cancer ends, or the skin cancer has recurred.

See nevus.

Nevus (pl nevi): What dermatologists call a “mole,” this usually pigmented skin lesion may be present from birth, but most often appears later in life. By age 3, approximately 80% of children will have at least one mole. There are dozens of different types of moles, of many shapes, colors, and sizes. Most moles are not cancerous. Occasionally, a
mole may become a cancerous growth.

Open biopsy: An incision is made in order to surgically remove tissue so that it may be examined under a microscope. This type of biopsy may be performed when a patient has melanoma and a lymph node near
a melanoma feels hardened or enlarged. The lymph node in question is surgically removed and examined
under a microscope to see if it contains melanoma cells.

Palliative care: Relieves symptoms and improve a patient’s quality of life, but does not treat the disease.

Precursor: A lesion that has the potential to develop into skin cancer.

Primary tumor: The first appearance of a tumor. In skin cancer, there may be multiple primary tumors.

Recurrent tumor: Tumor that was treated but has returned.

Regional: Cancer that has spread beyond the site of the primary tumor to nearby lymph nodes and sometimes
tissue/organs close to the primary tumor.

Risk factor: A attribute that increases the likelihood  that something will occur. Personal risk factors for skin cancer include fair skin, especially when combined with blond or red hair and blue, gray, or green eyes; long-term unprotected exposure to sunlight; tendency to freckle; tendency to sunburn rather than tan; atypical moles; and personal history of skin cancer.

lymph node biopsy
: A diagnostic surgical procedure used to find out if the melanoma has spread to the lymph nodes. It involves the surgeon identifying the first lymph node, known as the “sentinel node,” to receive lymph draining from the site of the primary tumor. The sentinel node is found by injecting radioactive material and/or
dye into the skin near the tumor and tracing the flow of lymph from the site of the tumor to the local and regional lymph nodes. Once the sentinel node is identified, it is surgically removed and sliced into sections for laboratory analysis to determine if cancer cells are present. Sometimes, the surgeon will remove two or three nodes.

Squamous cell carcinoma: Skin cancer that forms in the flat, scale-like skin cells of the epidermis called the squamous cells. It accounts for approximately 16% of all skin cancers. This cancer can metastasize and cause death.

Stage: How far the cancer has advanced. The staging process determines whether the cancer is confined to the
primary tumor or if it has progressed to the lymph nodes or distant organs.

Subcutis: Literally, this means “beneath the skin.” The subcutis also is defined as the bottom layers of skin. These layers consist mostly of fat cells. Blood vessels, nerve fibers, and muscle fibers also are found in the subcutis. Thickness of the subcutis varies throughout the body and depends on the amount of fat present. Therefore, the subcutis is much thinner on the eyelids than the buttocks.

Superficial spreading melanoma: See melanoma.

Thickness: In 1975, Alexander Breslow, MD, observed that the depth of a tumor (how deeply the tumor extends into the skin) correlates to the 5-year survival rate after surgical removal of the tumor. This has come to be known as “Breslow’s thickness,” which is documented in the table below:

Breslow Thickness (millimeters)

less than 0.76





more than 8.0


Ulceration: A break in the surface of a skin cancer tumor,  which is often only seen under the microscope. When such a break occurs, the tumor is said to be “ulcerated.”

Vaccine therapy: A type of immunotherapy. Still experimental, some patients with advanced melanoma are receiving a vaccine, which is similar to the vaccines that protect us against viruses, in hopes that the small amount of melanoma injected into the patient will enable the body to attack the melanoma.


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