A nevus (plural: nevi) is a benign (non-cancerous) skin lesion, commonly known as a mole or birthmark. It is formed by a cluster of melanocytes—the cells responsible for producing melanin, the pigment that gives color to the skin.
Nevi can be:
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Congenital (present at birth)
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Acquired (develop during life, especially in childhood or adolescence)
📚 Origin of the Term:
The word "nevus" comes from Latin — naevus, meaning birthmark or mole.
📌 Types of Nevi:
| Type of Nevus | Description |
|---|---|
| Common Melanocytic Nevus | Brown, round, smooth mole; flat or slightly raised |
| Congenital Nevus | Present at birth; may be large and hairy |
| Dysplastic Nevus | Irregular borders, uneven color; may resemble melanoma |
| Blue Nevus | Deep blue or black; due to deep pigment cells |
| Vascular Nevus (Hemangioma) | Reddish or purple; made of blood vessels |
| Hairy Nevus | Covered with hair, often on the trunk |
🧬 Causes of Nevus Formation:
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Genetics (runs in families)
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UV exposure (sunlight, tanning beds)
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Hormonal changes (puberty, pregnancy)
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Skin injury (rarely)
⚠️ When to Be Concerned: ABCDE Rule
Use the ABCDE method to watch for signs of melanoma (skin cancer):
| Letter | Meaning | What to Look For |
|---|---|---|
| A | Asymmetry | One half unlike the other |
| B | Border | Irregular, notched, blurred |
| C | Color | Multiple colors or uneven tone |
| D | Diameter | Larger than 6mm (pencil eraser) |
| E | Evolution | Any change in size, shape, or color |
If any of these are present, see a dermatologist immediately.
🧪 Diagnosis:
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Dermatoscopy — visual inspection with a magnifying tool
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Biopsy — sample of the nevus sent to lab for testing if suspicious
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Photography tracking — to monitor changes over time
💊 Treatment:
Most nevi are harmless and do not need treatment.
Removal is recommended if:
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There are changes suggesting cancer
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It is frequently irritated (shaving, rubbing)
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Cosmetic reasons
Removal methods:
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Surgical excision (with or without stitches)
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Laser removal (for cosmetic cases)
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Electrosurgery (burning off with electric current)
🛡️ Prevention Tips:
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Avoid excessive sun exposure, especially from 10 am to 4 pm
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Use sunscreen (SPF 30 or higher) every day
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Do not use tanning beds
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Regular skin checks — self-exam or by a dermatologist
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Take photos of large or suspicious moles to monitor changes
⚖️ Nevus vs. Melanoma – Key Differences:
| Feature | Benign Nevus | Melanoma |
|---|---|---|
| Growth | Slow or stable | Rapid |
| Color | Uniform brown | Multi-colored, uneven |
| Shape | Symmetrical | Asymmetrical |
| Border | Smooth and even | Irregular or blurred |
| Symptoms | Usually none | May itch, bleed, or crust |