What is a benign mole?
Most moles are benign or harmless. Moles are types of skin growths or lesions, commonly referred to as a nevus (plural: nevi). Nevus is a generalised medical term for a visible, circumscribed, chronic lesion which sits on the skin or mucosa. These growths can take the form of freckles, moles, skin tags and seborrheic keratoses.
Typically, moles are pink, brown or tan in color with a distinct border. Moles usually develop within the thick layer of living tissue below the epidermis (outer layer of skin), which contains blood capillaries, nerve endings, sweat glands, hair follicles, and other structures. Moles occur when cells in the skin grow in a cluster, forming a lesion, instead of being spread throughout the skin.
Some moles develop from cells are called melanocytes, which make the pigment that gives skin its natural color. They can also develop from other cells, including nevus cells.
Causes of benign moles
Moles can occur anywhere on the body. They can be present at birth, but it is possible for them to develop throughout one’s lifetime. People of all ages can be born with moles, or develop new ones of any size and color throughout their lifetime. In general, however, darker skin types usually have darker moles.
Most moles are made of cells called melanocytes which make a pigment called melanin. Melanin has two principal functions: it helps to protect the body from ultraviolet light (UV radiation) from the sun and gives skin and hair its natural color. People with darker complexions have more of these cells, and are more likely to develop new moles after exposure to sunlight.
Common types of benign moles
- Compound melanocytic nevi: These are usually raised above the skin, light brown and sometimes hairy.
- Dermal melanocytic nevi: These are usually raised, pale and sometimes hairy.
- Junctional melanocytic nevi: These are usually brown, round and flat.
A seborrheic keratosis is a kind of skin growth or lesion which usually appears as a brown, black or light tan growth on the face, chest, shoulders or back. They are usually melanocytic (melanin-containing, or pigmented). Seborrheic keratoses are common, and can be scaly, waxy and slightly raised above the skin (elevated). Although these growths are not themselves harmful, they can be difficult to distinguish from malignant melanoma, one of the most serious types of skin cancer, so it is advisable to have them checked to ensure that they are not, in fact, melanomas.
Good to know: If a keratosis becomes actinic, as in, red, scaly and swollen, this could indicate that it is precancerous. Actinic seborrheic keratoses, also known as solar keratoses, usually occur as a result of years of sun exposure. Any suspected actinic keratosis should be checked and removed by a doctor, because, although these lesions are not always malignant, they may develop into melanoma skin cancer if left untreated.
Atypical types of benign mole
Atypical moles are unusual-looking moles. They are also known as dysplastic nevi. Atypical moles may be mistaken for melanoma, but are not necessarily cancerous or precancerous. Even though an individual atypical mole may be benign, however, people who have them are at increased risk of developing melanoma, in a mole or elsewhere on the body. Common types of dysplastic nevi include:
- Blue nevus: Dark blue in color and can be flat or raised.
- Dysplastic or atypical nevus: Also known as “Clark nevi,” this is an unusual looking, slightly larger size of mole with an irregular border.
- Halo nevus: Surrounded by a white ring where the skin has lost its color.
Changes in benign moles
The appearance of moles can change over time. They can change in number and appearance and can also fade away over time. It is important to familiarise oneself with the lesions on one’s body so as to establish their size, shape and type(s) are normal, as this may be different for every person. This will make it easier to spot atypical lesions or changes to lesions, which could indicate melanoma.
Environmental factors such as exposure to sunlight, and hormonal changes such as going through puberty or pregnancy can cause moles to darken or develop. Changes in moles may require a visit to a doctor to determine if the mole is exhibiting dysplasia, i.e. becoming dysplastic. When a lesion becomes dysplastic, it contains abnormal cells or shows abnormal development. A mole becoming dysplastic may indicate the development of melanomas or carcinomas (cancerous cells).
Identifying cancerous moles
Melanoma is the most serious type of skin cancer. Melanomas develop from melanin-containing cells, called melanocytes. People with fair skin, red or blond hair or who spend a lot of time in strong sunlight are at higher risk of developing melanoma. It is important to avoid prolonged sun or other UV radiation exposure to reduce the risk of developing dysplastic or cancerous moles.
Good to know: The most common types of non-melanoma skin cancer are basal cell and squamous cell carcinoma. The typical warning sign of non-melanoma skin cancer or carcinoma is a growth or sore that doesn’t heal, which should be checked by a doctor.
To find out more about identifying melanoma, visit this resource on signs of melanoma. For more information about melanoma and basal or squamous cell carcinoma in general, visit this resource on melanoma, which discusses diagnosis, treatment and prevention.
Potential indicators that a mole is cancerous include:
Nevi with 3 or more different shades of brown or black are particularly likely to be dysplastic, indicative of melanoma or carcinoma. The following alphabetic mnemonic (ABCDE) is a useful way to remember the important indicators that an atypical nevus could be cancerous.
If a nevus suddenly begins to display any of the signs listed below, it is important to have it examined by a dermatologist:
- Asymmetry: Changing shape, in particular if lesions develop an irregular edge.
- Border: The border or edges of the nevus become ragged, blurred, or irregular.
- Color: Getting darker, becoming patchy or multi shaded; its color may have shades of tan, brown, black, blue, white, or red.
- Diameter: The nevus may get bigger; enlargement is especially concerning if its diameter becomes larger than the eraser of a pencil.
- Elevation/Evolution: The nevus may appear elevated, or raised from the skin, and may look inflamed, bleed or become crusty.
Visit a dermatologist (skin doctor) immediately if there are any noticeably atypical changes in a mole's color, height, size, or shape. It is also vital to have nevi checked if they bleed, ooze, itch, appear scaly, or become tender or painful.
If a dermatologist believes a melanocytic nevus needs to be evaluated further to find out whether it is cancerous, they will conduct a biopsy. This involves shaving or cutting it out so that it can be examined under the microscope. If an atypical nevus is found to contain cancerous melanocytes, the dermatologist will remove the entire mole or scar from the biopsy site by cutting out the entire area, as well as a rim of normal skin around it. They will then suture the wound (stitch the wound to close it). This treatment is carried out to ensure that any melanoma-containing cells are removed in their entirety, preventing melanoma from spreading elsewhere in the body.
Removing benign moles
Even though benign moles do not pose health risks such as melanomas, many people opt to have them removed. Most people who seek to have nevi removed do so for cosmetic reasons, for instance, if one is embarrassed about how a particular mole or moles look, or practical reasons such as if they snag on clothing or impede shaving.
Scarring is a possible consequence of removing a nevus. With scarring in mind, its location and the likely aesthetic development of the scar should be considered before removal, especially in cases where the procedure has been sought for cosmetic reasons.
Methods of mole removal include:
Common methods of removing nevi include burning them off with an electric current which passes through a wire that becomes hot and is used to burn off the upper layers of the skin. The heat helps prevent bleeding. More than one treatment may be needed to remove a nevus.
Alternatively, the nevus can be cut or "shaved" off the skin. Some nevi may have subcutaneous cells (which reside underneath the skin), so the doctor might need to make a deeper cut to remove the entire mole to prevent it from growing back. The cut may require stitches.
Nevi can also be frozen off with liquid nitrogen. The dermatologist will swab or spray a small amount of super-cold liquid nitrogen on the mole or skin tag. After it has been frozen off, there might be a blister at the site where it was, but this usually heals on its own.
By taking appropriate measures to avoid sun damage, a person can:
- Prevent new nevi from developing
- Prevent existing melanocytic nevi from developing melanoma skin cancer
When spending time in direct sunlight, always:
- Wear sunscreen with a high sun protection factor (SPF), such as SPF 50
- Use sun-protective clothing, such as wide-brimmed hats, sleeves and long pants
- Seek shade regularly
- Stay out of the sunlight between peak hours, (around 10am to 4pm)
Check the body several times per year, particularly after periods of sun exposure, for any new atypical moles or atypical changes to existing moles, which could indicate melanoma.
Benign mole FAQ’s
Q: Can a benign mole grow back after removal?
A: If a mole has been removed by cutting it off so that it is level with the skin, some cells may remain below the skin. These can act as a “seed” and cause it to regrow. It is not possible to predict whether it will grow back. The chances of this are greatly reduced if care is taken to remove the subcutaneous cells during the initial procedure.
Q: Can a benign mole become cancerous?
A: Melanomas can develop anywhere in the surface of the skin, including sites occupied by benign moles or within the melanocytic tissue of the mole itself. For this reason, it is important to consult a physician if a mole undergoes any changes, as these may be signs that it has become cancerous.
**Q: Can a benign mole change color? **
A: Yes. Most commonly, moles change color over time by getting darker after exposure to sunlight. This is not necessarily a cause for concern, but could indicate the presence of melanoma, so it is advisable to consult a doctor.