Introduction:
Moles (also referred to as nevus or nevi) are small benign growths on the skin. It could look like a small bump or just as big as a pimple that is present on the skin surface. Nevi are derived from melanocytes (pigment-producing cells that produce melanin) due to their proliferation. Nevus can be present either at birth (congenital nevus) or can appear at any time of life.
Clinically their characteristic appearance looks like a flat or round, small bumps-like structure with less irregular borders and exhibits colors like brown, black, blue, tan, or pink. It does not harm your body as it is always benign, but rarely can it become cancerous. Do examine your moles to find any unusual changes like swelling, redness, itching, etc. If you do find such changes, then consult your dermatologist to get a clear idea about the condition.
What Are the Common Types of Nevi?
Some of the common types of nevi are:
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Congenital nevus (mole that is present at birth).
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Dysplastic nevus (otherwise known as an atypical mole and has a high risk of developing into melanoma).
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Blue nevus (dome-shaped mole with colors ranging from blue-black to blue-gray. It can be either congenital or acquired).
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Miescher nevus (acquired dermal melanocytic nevus in which melanocytes infiltrate into the dermis).
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Reed nevus (dark pigmented melanocytic nevus characterized by the presence of spindle-shaped dermal melanocytes).
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Unna nevus (a type of intradermal nevus that resembles miescher nevus).
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Meyerson nevus (a condition in which the nevus is surrounded by eczema).
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Halo nevus (nevus surrounded by a white ring or halo).
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Spitz nevus (a rare type of nevus that typically appears before the age of 20).
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Agminated nevus (cluster of melanocytic nevi confined to a localized area on the skin).
What Is Blue Nevi?
The blue nevus is typically a mole that is benign (non-cancerous) in nature. More than one blue nevus is referred to as blue nevi. They are melanocytic nevus characterized by the presence of ovoid or spindle-shaped nevus cells (a variant of melanocytic cells). It is caused by the migration of melanocytes from the neural crest and due to its proliferation in the underlying dermis of the skin. These cells tend to go deeper into the skin (dermis) due to their proliferation. It can be present either at birth or can appear at any time in life. Blue nevi are named based on the blue color they exhibit, and this is due to the Tyndall effect when light is scattering shorter wavelengths by the melanin pigments present in the dermis of the skin.
Blue nevi can be seen in any part of the body; mostly, it is seen in the head and neck region, sacral area, feet, and hands. Clinically it appears like a flat or dome-shaped structure with a smooth surface. The color of the nevus may vary from blue-gray to blue-black. They are harmless and do not lead to any complications. However, in rare instances, cellular blue nevus (a type of blue nevus) may develop into malignant cellular blue nevus (a form of melanoma). If you have any moles in your body, do examine for any unusual changes like swelling, inflammation, itchiness, and ulceration. Do consult a dermatologist if you find any such abnormal changes.
Who Is More Likely to Get Blue Nevi?
Blue nevi can be present at birth (congenital nevus), or it can appear at any time of life. It is more commonly seen in women than men. Asians are more likely to be affected by blue nevi.
What Are the Different Types of Blue Nevi?
The different types of blue nevi include:
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Common blue nevus (benign nevus that does not lead to any complications).
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Cellular blue nevus (a type of blue nevus that can rarely develop into malignant blue cell nevus).
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Amelanotic blue nevus (a variant of blue nevus that is minimally pigmented)
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Combined blue nevus (a rare melanocytic lesion that contains more than two melanocytic nevus components from a cytological point of view).
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Epithelioid nevus (rare melanocytic nevus characterized by the presence of polygonal epithelioid cells).
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Subungual blue nevus (a type of blue nevus that mostly affects the fingers, especially the thumb or the hallux of women).
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Sclerosing (desmoplastic) blue nevus (an uncommon type of blue nevus characterized by an amorphous blue appearance around the edges of the nevus and hypopigmented at the center).
What Is the Difference Between Common Blue Nevi and Cellular Blue Nevi?
The most common variants of blue nevus include common blue nevi and cellular blue nevi. Common blue nevi are a benign form of blue nevus which exhibits a characteristic appearance of a flat or dome-shaped structure. The color of the lesion may vary from blue-gray to blue-black. The size of common blue nevus ranges from 0.5 to 1cm.
Cellular blue nevus differs from common blue in appearance. The size of the cellular blue nevus is larger than the common blue nevus (larger than 1cm in diameter). It can grow larger with time, and the surface gets ulcerated as it grows. Cellular blue nevus can rarely develop into malignant blue cell nevus (a form of melanoma).
What Are the Clinical Features of Blue Nevus?
The clinical features of blue nevus are the following;
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Solitary flat or dome-shaped macule or papule or plaque with a smooth surface.
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The color of the nevus varies from blue-gray to blue-black.
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It can be found anywhere on the body; mostly, it is found over distal extremities (dorsum of hands and feet), head and neck region, face, etc. In rare cases, blue nevus is found in the vagina, cervix, oral mucosa, and prostate.
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The size of common blue cellular nevus ranges from 0.5 to 1cm, and they are benign.
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The cellular blue nevus is a variant of blue nevus, which can rarely develop into malignant blue cell nevus. The size of cellular blue nevus is greater than 1 cm.
How Is Blue Nevi Diagnosed?
The blue nevus is diagnosed with the help of a skin doctor (dermatologist). A dermatologist will conduct a clinical examination primarily to diagnose blue nevi by assessing the clinical features. To have an accurate diagnosis, the dermatologist may suggest further diagnostic measures. It includes;
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Dermatoscopy: Dermatoscopy is a non-invasive diagnostic technique used to examine pigmented skin lesions. It requires a dermatoscopy (a powerful lighting system) and a high magnifying lens to examine lesions. Recent advancements in dermatoscopy use computer software to archive images obtained through dermatoscopy that aids inaccurate diagnosis.
- Histopathological Examination: A dermatologist may suggest for histopathological examination to delineate the presence of underlying cells in the nevus. Histopathological examination of blue nevus reveals the presence of spindle-shaped melanocytes inside the dermis.
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Excisional Biopsy: An excisional biopsy may be suggested by a dermatologist in case of any suspicious lesion to have a much more accurate diagnosis. It helps in determining any malignant transformation of blue nevus, which rarely occurs. In an excisional biopsy, a healthcare provider will remove either an entire lump or area of abnormal skin along with some normal healthy tissue. Stitches are required to close the site of excision. The removed tissue is sent for microscopic examination to detect any malignant changes.
How Is Blue Nevi Treated?
The blue nevus is usually a birthmark that is harmless and does not require any treatment. But it may persist lifelong if it is left untreated. Surgical excision may be carried out in cases of suspicious lesions which can exhibit malignant potential. Some persons may undergo surgical excision of blue nevi for cosmetic reasons.
What Is the Differential Diagnosis of Blue Nevi?
The differential diagnosis of blue nevi include;
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Melanoma (skin cancer that develops from melanocytes).
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Kaposi's sarcoma (cancerous tumor of connective tissue).
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Dermatofibroma (a common cutaneous nodule).
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Traumatic tattoos (undesirable tattoos caused by different foreign bodies like sand, metal, etc.).
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Combined nevus (a combination of blue nevus and compound melanocytic venus).
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Cutaneous metastasis.
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Thrombosed plantar wart (painful warts on the soles of the feet).
Conclusion:
The blue nevus is a benign melanocytic nevus that can either be present at birth or can appear at any time of life. It is harmless and does not require any treatment. But it may persist lifelong if left untreated. Blue nevi rarely develop into malignant blue cell nevus, which needs to be treated. A dermatologist may help in managing and treating the condition.
