What is Blue Nevus?
“Blue nevus” is a term for a collection of skin changes that involve an abnormal growth of pigment-producing cells known as melanocytes in the skin. These changes show up as blue to black lumps on the head, arms and legs, or buttocks. Most of the time, these are acquired (developed over time) and appear as a single lump, but they can also be present from birth and show up at multiple places on the body. The two widely recognized types based on their microscopic appearance are the common blue nevus (also known as dendritic blue nevus or Jadassohn-Tieche type) and the cellular blue nevus. Some of the less common versions of blue nevus include those that contain skin-cell like cells (epithelioid), those with excessive connective tissue (sclerosing), those without pigment (amelanocytic), and combined types.
What Causes Blue Nevus?
Blue moles, also known as blue nevi, are commonly something you develop over time. However, in some unusual cases, people can be born with them. They can also be linked with certain family traits or other kinds of health conditions. Two of these conditions are LAMB, which stands for moles, heart growths, and blue nevi, and NAME, which stands for moles, heart growths, nerve growths, and freckles.
There is a particular type of blue nevus, known as the epithelioid type. This type is commonly seen in a health condition called the Carney complex. The Carney complex is a category of disorders that impact multiple hormone-producing glands. It is characterized by dark colored skin and mouth sores as well as growths in the heart.
Risk Factors and Frequency for Blue Nevus
The two most common types of blue nevus, Common and Cellular, occur in different groups of people and have different characteristics. Common blue nevus generally appears in young adults, while cellular blue nevus is most often diagnosed in middle-aged people and is more than twice as common in women than in men. Size is another distinguishing factor, cellular blue nevus can be up to several centimeters in size, while common blue nevus typically doesn’t exceed 1 cm.
- Common blue nevus usually shows up in young adults.
- Cellular blue nevus is commonly diagnosed in middle-aged individuals and is more common in women than men by a ratio of 2:1.
- Cellular blue nevi can reach several centimeters in size.
- Common blue nevi typically don’t measure more than 1 cm.
Signs and Symptoms of Blue Nevus
Blue nevi, or moles, typically appear as a single, clearly defined, blue to black lump or several lumps clustered together at one site. They may also spread out in some inherited conditions known as NAME and LAMB. Commonly, blue moles are found on the face and limbs, while the cellular type of blue moles usually appear on the buttocks and the base of the spine.
It’s also possible, though less common, for blue moles to appear in other places outside of the skin. This includes areas such as
- the lining of the eyelids (conjunctivae)
- the lining of the mouth (oral mucosa)
- the digestive tract (gastrointestinal tract)
- the urinary and reproductive tract (genitourinary tract)
- under the fingernails or toenails (subungual)
Testing for Blue Nevus
A blue nevus is typically diagnosed by examining the skin directly or using a special skin examination tool called a dermatoscope. However, the most reliable way to confirm the diagnosis is through a biopsy, which is a procedure where a small sample of the skin is removed and examined under a microscope.
No other standard tests like lab tests or imaging scans are usually needed for diagnosing a blue nevus. It’s important to distinguish it from melanoma, another type of skin growth that can sometimes look similar. Melanoma often appears as a lump with a blue or black colour.
One common method to distinguish these conditions is to look for “ABCDEs.” This stands for asymmetry (one half of the growth looks different than the other), borders (irregular or poorly defined edges), color (varying colours within one growth), diameter (bigger than 6mm), and evolving (changes in size, shape, or colour).
Another useful tool is the “Ugly Duckling” sign. This technique is based on the idea that suspicious skin growths usually look different from the surrounding skin. Using these two methods together may increase the chances of correctly diagnosing the condition.
If there’s a high suspicion of melanoma, a specific type of biopsy, an incisional biopsy, should not be used. Instead, an excisional biopsy is recommended, where the entire growth is removed (except in some cases such as larger growths or those in areas that are cosmetically sensitive). This type of biopsy can provide more accurate information about the stage of the tumor if it is malignant and allows for immediate referral for the appropriate treatment.
Treatment Options for Blue Nevus
Blue nevi, a type of skin mole, can sometimes be mistaken for a more serious condition called blue nevus-like melanoma, which is a form of skin cancer. Because of this, it’s important to keep an eye on these moles and check for any rapid changes in their shape or size. This is particularly important for a specific type of blue nevus called cellular blue nevus, which can potentially develop into malignant blue nevus.
If there are any suspicious changes, a skin sample (biopsy) should be taken to check for cancer cells. The most effective way to remove a blue nevus is through a procedure called excision, which involves cutting out the mole. However, if the mole is stable and not changing, it’s usually enough just to monitor it over time.
In some rare cases, a blue nevus can return at the same spot where it was previously removed. If this happens, a new biopsy or another excision may be recommended. This is to ensure that the returning mole is not a sign of malignant blue nevus or other forms of melanoma, which is a type of skin cancer.
What else can Blue Nevus be?
Blue nevi are particular types of skin marks that can often be mistaken for other skin conditions. A rare type of blue nevus that doesn’t contain melanin, called an amelanocytic blue nevus, might be mistaken for a dermatofibroma or a scar. Its similar appearance is due to the presence of spindle cells, collagen, or a hardened type of tissue called sclerotic stroma. It might also be confused with a type of skin cancer known as amelanocytic melanoma.
Another variant of blue nevus, called a desmoplastic blue nevus, is characterized by excessive fibrous tissue in the skin. Due to this, it can also be mistaken for a particular type of melanoma, known as desmoplastic melanoma.
It’s very important to correctly distinguish between similar-looking skin conditions. For instance, a serious condition known as blue nevus-like melanoma needs to be accurately identified and not confused with blue nevi, particularly the cellular subtype. Misidentification can often lead to a delay in diagnosis and treatment.
What to expect with Blue Nevus
The outlook for a blue nevus, a type of skin lesion, is generally positive because it is typically harmless. However, there is a rare but serious condition when a blue nevus can turn into a type of skin cancer called melanoma. In most known cases, this type of melanoma has turned out to be aggressive, leading to the spread of cancer cells to other parts of the body and even death.
An in-depth analysis has found that this specific type of melanoma, originating from a blue nevus, carries a risk of spreading and an outlook similar to a standard melanoma. This comparison holds when we look at lesions of equivalent depth and staging, which means comparing melanomas that are at similar levels of penetration into the skin and stages of development.
Possible Complications When Diagnosed with Blue Nevus
Generally, benign blue nevi, which are a type of mole, do not come with any significant complications. On rare occasions, these benign moles can become malignant (cancerous), or new melanomas (skin cancer) can develop. This carries the risk of the cancer spreading to other parts of the body, but it is not common.
Common Risks:
- None in benign blue nevi
- Rare risk of turning malignant (cancerous)
- Rare occurrence of new melanoma developing
- Rare risk of cancer spreading to other parts of the body
Preventing Blue Nevus
Blue nevi, or small blue-colored spots on the skin, are typically harmless. If these spots do not change in size, shape, or color, there’s usually no need for a biopsy, a procedure where a small sample of skin is removed for examination. However, if these spots are new or show changes, a biopsy may be recommended. This is to rule out conditions that may look like blue nevi but could actually be a type of skin cancer called melanoma.
