There are black spots on the body, some are pigmented nevi, some are spots, and some are melanomas that are malignant tumors.
So how can you tell the difference between these dark spots? Which ones are benign and which ones are malignant? Does the "black mole" on the body have to be removed? These are all questions that dermatologists often ask in the outpatient clinic.
Let's talk about these common questions about moles in turn.
What is a melanocytic nevus? What is the difference between it and dark spots?
A pigmented nevus, also known as a melanocytic nevus, is a common benign tumor of the skin made up of nevus cells.
Nevus cells are a special type of skin melanocytes that produce large amounts of melanin and remain in the cells, resulting in pigmented nevi that are usually dark black or dark brown.
Mole cells grow in nests in the subepidermal layer of the skin or in the dermis, forming what we can see with the naked eye. Nevus cells have the ability to divide and mature and differentiate, and can develop new or gradually expand under certain environmental stimuli.
What we often call "freckles" or "sunspots" usually comes from melanin clumps "secreted" by basal layer melanocytes.
Melanocytes synthesize melanin increases after sun exposure, which leads to the accumulation of pigment particles on the surface of the skin, and the more obvious the pigmentation is, which usually needs to be treated by photoelectric and chemical peels.
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The biggest difference between superficial pigmented spots and melanocytic nevi is that most superficial pigmented spots are clumps of melanin granules, which have no cellular components in most cases and are basically non-malignant for life.
However, a small number of nevi are at risk of turning into malignant melanoma, so it is necessary to observe the pigmented nevus for signs of malignant transformation for a long time.
How do melanocytic nevi come about?
It is generally believed that the most common factors that contribute to the formation of melanocytic nevi include genetic factors, UV exposure, skin phenotype, immunosuppression, hormonal changes in the body, and more.
1. Genetic factors
Clinically, it can be observed that if parents are prone to pigmented nevi, the proportion of children inherited is very high, and even several genes have been found in the genetics that will affect the number and shape of moles.
2. Sun exposure/UV exposure
The intensity of prolonged sun exposure during childhood can affect the formation of moles, particularly high-intensity, prolonged sun exposure or intermittent sun damage.
3. Skin phenotype
There is literature suggesting that light-skinned individuals may be more susceptible to pigmented nevi, particularly in Caucasian adolescents.
3. Immunosuppression
There have been reported in the literature that an increase in the number of moles has been observed after weeks to months of treatment in people using immunosuppressants and some biologics.
4. Hormonal changes
Changes in hormone levels, such as during puberty and pregnancy, can be observed with more new pigmented nevi throughout the body, or the original pigmented nevus may become larger.
In addition, some areas that have been repeatedly irritated, such as areas that have been repeatedly rubbed and damaged, may lead to the formation of pigmented nevi.
Once the nevus cells are induced to differentiate and aggregate at the epidermal and dermal junction of the skin under the influence of the above factors, multiple nest-like structures are quickly formed, resulting in the appearance of new melanocytic nevi that we can see with the naked eye.
Newly-formed nevus cells can be found in the lowest layer of the epidermis (stratum corneum) and dermis. As the nevus cells gradually mature and differentiate, these nevus cells will slowly "sink" into the dermis layer of the skin, and gradually mature and differentiate.
What are the types of pigmented nevi? Which is the safest?
Pigmented nevi are mainly divided into congenital melanocytic nevi and acquired melanocytic nevi.
1. Congenital melanocytic nevus
Congenital melanocytic nevi are mainly defined as visible nevi that are present at birth or appear within a few months of birth.
The classification is mainly based on the diameter of the rash divided into:
- Compact < 1.5cm.
- 中型–M1型1.5~10 cm；M2型10~20 cm。
- 大型–L1型20~30 cm；L2型30~40 cm。 在新生儿中，大型CMN在头部>9 cm或在躯干>6 cm。
- 巨型–G1型40~60 cm；G2型>60 cm。
Among them, the lifetime risk of melanoma in patients with small and medium-sized congenital melanocya is less than 1%, and the lifetime risk of melanoma (cutaneous or extracutaneous) in patients with large/giant congenital melanocytic nevi is estimated to be 2%~5%.
Therefore, according to the size of the black mole after the birth of the child, it is necessary to see a dermatologist regularly to assess the risk of this type of rash, and if necessary, surgical excision and pathological examination.
2. Acquired melanocytic nevus
Acquired melanocytic nevi are often classified according to the different locations where the nevus cells are located, and clinical melanocytic nevi are usually divided into three types: junctional nevus, intradermal nevus, and mixed nevus.
交界痣（Juctional）
Usually located at the junction of the epidermis and dermis, neonevi tend to appear on the palms, soles of the feet, lips, and genitalia, and are usually dark brown to black in color, sometimes with darker pigmentation in the center than at the edges.
Because of the distribution site, easy to be rubbed repeatedly, and the relatively early differentiation characteristics, this part of the pigmented nevus may be cancerous.
皮内痣（Dermal）
The nevus cell nest is located within the dermis, in which multinucleated nevus cells are visible. Normally, these mole cells have matured and differentiated and stop producing new melanin.
As a result, intradermal nevi often appear as skin-colored to yellowish-brown papules, dome-shaped, papillary, or pedunculated, soft and elastic, which is commonly known to many as "fleshy nevi", and most hairy moles are seen in this condition. This part of the pigmented nevus is basically not malignant.
混合痣（Compound）
It has the characteristics of both intradermal nevi and residual junctional nevi, which is a hybrid form of the above two types of nevi and can be seen throughout the body.
Mixed moles range in color from tawny to dark brown, and the more symmetrical and consistent the color (especially if they are yellowish brown to moderately brown), the less likely they are to worry.
How can you tell if a mole will become cancerous? How to distinguish a mole from melanoma?
Determining whether a pigmented nevus is malignant is a situation that requires a professional dermatologist to combine dermoscopic examination, dermatopathological examination, regular follow-up observation and other comprehensive judgments.
However, for many readers with non-medical backgrounds, you can learn about the ABCDE rule and conduct some self-tests on some special parts or melanocytic nevi that are repeatedly easy to be irritated, which will help you seek help from a dermatologist in the first place.
ABCDE Rule
The ABCDE is a widely used self-test for melanocytic nevi and melanoma to identify risk, with each letter representing a feature to look out for:
A (Asymmetry) asymmetry: Benign melanocytic nevi are usually symmetrical, whereas malignant melanoma tends to be asymmetrical in shape.
B (Border): Benign melanocytic nevi have clear and regular borders, while malignant melanoma rash borders tend to be blurred and irregular.
C (Color) color: Benign melanocytic nevi are uniform in color, malignant melanoma is usually uneven in color, may be different shades of color, and may even have multiple colors.
D (Diameter) diameter: Malignant melanoma is usually larger than 6 mm in diameter, but not all melanocytic nevi larger than 6 mm are malignant, and these benign large nevi require regular follow-up observation.
E (Evolution) progression: benign melanocytic nevus usually remains unchanged for a long time, while malignant melanoma may grow rapidly, or change in color, shape, and size, usually every 2~3 months to take pictures and observe and record, you can clearly see this part of the progression changes, once you find this rapid progression and change of "melanocytic nevus", you need to seek help from a dermatologist as soon as possible.
Beware of these situations
Melanocytic nevi in some relatively special locations need to be paid special attention to, such as pigmented nevi located in the oral mucosa, eyelid mucosa, vulva, palms, soles of feet and nails, etc., the probability of malignant transformation of this part of melanocytic nevus is relatively high, and it is necessary to observe and record changes regularly, and if necessary, it can be removed and treated early.
In addition, if there are symptoms such as bleeding, ulceration, itching and pain in the pigmented nevus, or many small moles suddenly appear around the large melanocytic nevus, it is also best to see a dermatologist as soon as possible, and the doctor may use skin biopsy and other methods for further examination and diagnosis.
Is there a cause for concern about melanin nevus hair? Can I just unplug it?
Melanocytic nevus hair growth is a common phenomenon, usually because the clump of mole cells is located just near the hair follicle, and the hair grows out of the hair follicle instead of the mole cell clump, and the two can coexist without affecting each other.
Most often, pigmented nevi with long hairs are more common in intradermal nevi and are usually predominantly benign and do not require additional hair treatment.
If you want to remove the hair from a pigmented nevus directly, it usually does not cause damage to the mole itself as long as it is done properly.
However, it is important to note that frequent or rough plucking may cause local irritation or inflammation, which may affect the appearance of the mole or cause bleeding and recurrent irritation in the pigmented nevus area.
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Gentle methods, such as scissor trimming, and avoiding direct extraction, are often recommended to reduce irritation of the mole.
However, if there are a large number of melanin nevi distributed in the beard area of men, repeated shaving may cause irritation to this part of the pigmented nevus, and it is necessary to pay closer attention to whether there are changes in this part of the pigmented nevus.
What can I do to get rid of a mole?
There are a variety of methods that can be used to remove moles in clinical practice, and each method has its specific indications, advantages and disadvantages, and precautions.
Here are some common ways to get rid of moles:
1. Laser Treatment/Electrocautery
Laser treatment is one of the most commonly used methods for mole removal in modern times, mainly by carbon dioxide laser and high-frequency electric laser.
It is often suitable for superficially pigmented nevi with a diameter of less than 2~3 mm. Electrocautery uses an electric current through electrodes to cauterize the necrotic tissue, causing it to die and fall off.
Advantages of this type of treatment:
- The pace of treatment is fast and the recovery period is relatively short.
- The pain is small and generally tolerable.
- Precise control of the depth of treatment reduces the risk of scarring.
Disadvantages of this type of treatment:
- Larger or deeper moles may require multiple treatments.
- It may take about 1 week for the wound to recover after treatment.
- After treatment, you need to pay attention to sun protection and keep the wound dry.
- Specimens of moles cannot be left for pathological examination.
2. Chemical corrosion/liquid nitrogen cryotherapy
The use of specific chemicals (e.g., trichloroacetic acid solution) to corrode melanocytic nevi is the most common "spotting" method in non-healthcare settings.
Cryotherapy usually uses liquid nitrogen to freeze melanocytic nevi so that they scab over and fall off, which is one of the mole removal methods that can be performed in medical institutions.
Advantages of this type of treatment:
- The price is low and the operation is simple.
- It is suitable for moles with a diameter of less than 5 mm, a light position and a light color.
Disadvantages of this type of treatment:
- It is difficult to accurately control the depth and scope of treatment, and it is easy to form scarring later.
- It does not work well for deeper moles.
- It is easy to leave melanocytes behind, which may lead to the recurrence of moles.
- Specimens of moles cannot be left for pathological examination.
3. Surgical excision
Surgical excision is the surgical removal of a melanocytic nevus completely.
Advantages of this type of treatment:
- It is suitable for moles with a diameter greater than 5 mm, a deep location, and an unknown nature.
- Pigmented nevi can be removed in one go to avoid recurrence.
- The excision of a pigmented nevus can be pathologically diagnosed to determine whether it is benign or malignant.
Disadvantages of this type of treatment:
- Longer recovery time: The stitches are removed about a week after the excision, and some of the scars may take six months to a year to gradually fade after the stitches are removed.
- Post-local anesthetic treatment is required.
You can weigh the pros and cons and discuss with your dermatologist before deciding on a treatment plan.
Most of the relatively small melanocytic nevi can still be removed by the first and second types of methods, but there are pigmented nevi with relatively high risk, relatively large, special location, and need pathological detection, and it is not recommended to find a random institution to spot the nevus, so as not to cause recurrence or stimulate the malignant transformation of melanocytic nevus.
Will there be a scar after mole removal? Will it recur?
Whether there will be scarring and recurrence after mole removal depends on the mole removal method, the type and size of the mole, the individual's ability to recover their skin, and the care after treatment.
In principle, all mole removal treatments carry the risk of scarring, but after a professional dermatologist evaluates the risk of pigmented nevus, and chooses the appropriate treatment according to the size, depth and location of the mole, the risk of scarring and recurrence can be effectively reduced.
Regular follow-up after treatment can also detect signs of mole recurrence in time and take appropriate measures.
If you are considering treating an existing melanocytic nevus, it is recommended to consult a professional dermatologist to understand the most suitable treatment plan for you before proceeding with relevant treatments.
| Reviewers
Zhong Hua
Zhuo Zheng dermatologist
Doctor of the Army Medical University
Visiting scholar at MD Anderson Cancer Center, USA
本文授权转载自卓正科普Health Express（D-HealthExpress），如需转载请联系 [email protected]。