Moles are benign (noncancerous) growths of the skin caused by the proliferation of melanocytes, which produce the dark protective pigment in the skin called melanin. Most moles appear in individuals during their 20s, though some may appear later in life and some may be present at birth. The number of moles peak in individuals during their 30s and have a tendency to decrease in number thereafter. Factors that determine the number of moles include familial or genetic predisposition and sun and ultraviolet light exposure.
A congenital nevus is a mole present at birth. Most of these moles are small, the size of a pencil eraser, dome-shaped, and may have some hair within [Figure 1]. Large congenital nevi, several inches across in an adult, have a higher tendency to develop into malignant melanoma.
Moles that appear after birth are called common acquired melanocytic nevi (moles).
There are three types of acquired moles:
- The flat mole or junction nevus [Figure 2]
- The dome-shaped mole or compound nevus [Figure 3]
- The raised mole or intradermal nevus [Figure 4]
They vary in size from a pinhead to a pencil eraser. The brown color may vary in shade, but it is usually uniform within individual mole. Moles may darken with sun exposure. They may also get darker and larger during the teen years, during pregnancy, and while taking birth control pills. Each mole has its own growth pattern. At first, moles are flat, pink, brown, or black in color. Over many years, moles slowly change and become more raised. Some moles will gradually disappear. These changes occur slowly during a lifetime. The average number of moles in an adult between 30 and 40 years of age is approximately 10 to 40 on the entire skin surface.
Some moles may be larger than average (larger than a pencil eraser) with irregular shape, and uneven color with darker brown centers and lighter, sometimes reddish, uneven borders. These moles are call dysplastic or atypical moles, which are often inherited [Figure 5]. Individuals with dysplastic moles have a greater risk of developing an aggressive type of skin cancer called malignant melanoma.
Why is it important to know about benign moles?
A benign mole can sometimes develop into skin cancer. Skin cancer arising from a benign mole is malignant melanoma, which is a very dangerous type of skin cancer that can be fatal if not treated early. The best way to survive malignant melanoma is to diagnose and treat it early. The best way to diagnose it early is to perform a weekly skin self-exam and to be suspicious about any new mole, changing mole, or mole that looks different or unusual from those in the surrounding area. If any mole looks suspicious, you should report it immediately to your dermatologist.
Malignant melanoma can arise from a benign mole, or a dysplatic mole, or from normal-appearing skin. Therefore, it is important to be familiar with all of your moles and to remember if a mole was there or not and what it looks like. Your weekly skin self-exam will help you familiarize and remember what your moles look like. If you see any new mole, changing mole, or a mole that looks different or unusual from those in the surrounding area, report it immediately to your dermatologist. Malignant melanoma can develop tomorrow or anytime in the future, so make sure you perform a weekly skin self-exam throughout your life.
Anyone can get malignant melanoma, but there are certain risk factors that make some individuals more susceptible to malignant melanoma than others. Risk factors increase your susceptibility to malignant melanoma; however, they do not mean you will develop malignant melanoma.
Risk factors for malignant melanoma include
- Personal and family (genetic) history
- Fair skin with red hair and blue eyes
- Male over 50 years old
- Increased number of moles: having more than 50 moles increases the risk of malignant melanoma
- Having atypical or dysplastic moles
- Personal history of malignant melanoma
- Family history of malignant melanoma, such as a parent, brother, sister, aunt, or uncle
- Environmental exposure
- Excessive long-term sun and ultraviolet light exposure
- Fair skin and having grown up in a southern region
- Frequent exposure to outside work or recreation
- History of multiple sunburns
- Use of an indoor tanning lamp or bed
- Medical condition that suppresses the immune system, such as AIDS or medications that organ transplant recipients take to suppress their immune system
- Excessive long-term sun and ultraviolet light exposure
How is malignant melanoma diagnosed?
Inspection of your skin by your dermatologist can confirm whether or not a mole is suspicious for malignant melanoma. Normal moles are easily diagnosed by your dermatologist with just a simple inspection of your skin. If your dermatologist determines that a mole is suspicious for malignant melanoma then a biopsy will be performed. This is a simple procedure performed in the office under local anesthesia. Your mole will then be sent to a pathology lab where thin sections from the mole will be examined under a microscope by a dermatopathologist (a dermatologist or a pathologist trained in the microscopic examination of skin lesions). In the event your biopsy confirms malignant melanoma, your dermatologist will discuss treatment options.
Inspection of your skin at home with a weekly skin self-exam can help you identify a suspicious mole and help your dermatologist diagnose malignant melanoma early. [Table 1] When inspecting your skin for any moles, growths, or spots, look for these signs.
New Changing Different and/or unusual
When inspecting your skin for any moles, growths, or spots, look for these signs.
Be suspicious of any new mole, changing mole, or mole that looks different or unusual from those in the surrounding area. If any mole is suspicious, you should immediately report it to your dermatologist as some aggressive types of malignant melanoma can spread inside your body within a few months.
When inspecting a single mole, only if you know it is a mole, it is helpful to apply the ABCDE rules to determine whether or not it is suspicious. [Table 2]
Normal Suspicious Asymmetry Border Color Diameter Evolving
Asymmetry: malignant melanoma has one half not matching the other half in size, shape, color, or thickness
Border irregularity: malignant melanoma has irregular edges that are notched, ragged, or scalloped
Color: malignant melanoma has a variety of colors within the same lesion, including shades of dark black and dark brown mixed with lighter tones; sometimes it may be red, pink, white, or skin colored
Diameter: malignant melanoma is larger than some surrounding moles, often greater than 6 millimeters or the size of a pencil eraser; however, malignant melanoma is less than 6 millimeters when it first appears
Evolving: malignant melanoma continues to grow and change, while other benign moles remain the same
The majority of moles are benign. Occasionally, a mole may become irritated by shaving or by clothes rubbing. Irritation such as shaving will not cause a mole to become malignant melanoma; however, if a mole is bleeding and you are not sure why then you should check with your dermatologist. An individual may want to have a mole removed that is frequently irritated or unattractive. Procedures to remove moles are short office visits that can be performed under local anesthesia in your dermatologist’s office. Your dermatologist will discuss the most appropriate treatment for you. Sometimes a mole will reappear after it is removed. A mole that reappears after it is removed should be carefully re-examined by your dermatologist. When a benign mole is removed, it should also be sent for microscopic examination to ensure that it is not malignant melanoma.
Patients diagnosed with multiple moles should be examined by their dermatologist at least once a year. Remember, individuals with multiple moles (more than 50) are more likely to develop malignant melanoma. Your dermatologist will inspect your skin for any new moles and will ensure that any previously treated moles are not growing back.
Patients with multiple moles should also perform a weekly skin self-exam. Learning what malignant melanoma looks like may help you identify a suspicious mole earlier.
If you cannot see some part of your body, ask your partner or a family member to assist you with your weekly skin self-exam.