Written by Ada’s Medical Knowledge Team
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. They can take many different forms, including 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 spreading out across 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. The Ada app can help you check your symptoms. Download the free app or find out more about how it works.
Types of benign moles
The most common types of benign mole include:
- Compound melanocytic nevi, which are usually raised above the skin, light brown and sometimes hairy.
- Dermal melanocytic nevi, which are usually raised, pale and sometimes hairy.
- Junctional melanocytic nevi, which 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 blemish on the face, chest, shoulders or back. They are usually melanocytic, i.e. 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.
Red, scaly and swollen keratoses
If a keratosis becomes actinic, i.e. 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 moles are also known as dysplastic nevi, and the term describes unusual-looking moles.
Atypical moles may be mistaken for melanoma, but are not necessarily cancerous or precancerous. However, even though an individual atypical mole may be benign, people who have dysplastic nevi are at increased risk of developing melanoma compared to those who do not. Melanoma can develop in a mole or elsewhere on the body.
Common types of dysplastic nevi include:
- Blue nevus, which is dark blue in color and can be flat or raised.
- Dysplastic or atypical nevus, which is also known as “Clark nevi,” this is an unusual looking, slightly larger size of mole with an irregular border.
- Halo nevus, which is urrounded by a white ring where the skin has lost its color.
Causes of benign 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.
Moles can occur anywhere on the body. They can be present at birth (congenital), but it is possible for them to develop throughout one’s lifetime (acquired). People can be born with moles, or develop new ones of any size and color throughout their lifetime, at any age. In general, however, darker skin types usually have darker moles.
Changes in benign moles
Environmental factors such as exposure to sunlight, and hormonal changes such as going through puberty or pregnancy can cause moles to darken or develop.
Therefore, the appearance of moles can change over time. They can change in number and appearance and can also fade away. 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.
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, this is a sign that it contains abnormal cells or may be undergoing 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.
Potential indicators that a mole is cancerous include:
Nevi with three or more different shades of brown or black are particularly likely to be dysplastic, indicative of melanoma or carcinoma. The alphabetic mnemonic (ABCDE) is a useful way to remember the important indicators that an atypical nevus could be cancerous:
- 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.
If a nevus suddenly begins to display any of these signs, it is important to have it examined by a dermatologist; a doctor who specialises in conditions that affect the skin. 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, i.e. 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 mole. 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.
Common methods of removing nevi include:
Burning moles 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 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 FAQs
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. You can also use the free Ada app to check your symptoms.
"Pathology of dysplastic (atypical) melanocytic nevi." Medscape. 27 December 2015. Accessed: 31 October 2018. ↩ ↩