Medical Term for a Mole
The medical term for a mole is "nevus" (plural: nevi), which refers to a benign pigmented lesion composed of nevomelanocytes grouped into nests located in the epidermis, dermis, or both.
Types of Nevi (Moles)
Moles can be classified based on their location in the skin:
- Junctional nevus: Nevomelanocytes located in the epidermis
- Dermal nevus: Nevomelanocytes located in the dermis
- Compound nevus: Nevomelanocytes present in both epidermis and dermis 1
Cellular Origin and Development
- Nevomelanocytes are derived from either epidermal melanoblasts or dermal Schwann cells
- Melanocytes are pigment-producing cells that originate from the neural crest
- These specialized cells produce melanin, which is packaged in organelles called melanosomes
- Each epidermal melanocyte secretes melanosomes to approximately 36 adjacent keratinocytes, forming an "epidermal melanin unit" 1
Natural History of Nevi
- Acquired melanocytic nevi (AMN) typically first appear around 1 year of age
- They peak in number during the second or third decades of life
- They tend to disappear by the seventh to ninth decades of life 1
- Moles may appear suddenly or become more prominent in response to:
- Sun exposure
- Hormonal changes (puberty, pregnancy)
- Certain medications (cortisone, corticotropin)
- Blistering diseases
- Chemotherapy
- Immunosuppression 1
Clinical Significance
Atypical Moles
Atypical moles (dysplastic nevi) are benign pigmented lesions that exhibit some clinical and histologic features similar to melanoma:
- Size ≥6 mm at greatest dimension
- Color variegation
- Border irregularity
- Pebbled texture 2
Risk of Malignant Transformation
The risk of any particular mole transforming into melanoma is very low:
- For individuals younger than 40 years: ≤0.0005% annually (≤1 in 200,000)
- For men older than 60 years: 0.003% annually (about 1 in 33,000)
- Lifetime risk for a 20-year-old: approximately 0.03% (1 in 3,164) for men and 0.009% (1 in 10,800) for women 3
Monitoring and Evaluation
The ABCDE criteria help identify potentially concerning moles:
- Asymmetry
- Border irregularity
- Color unevenness
- Diameter ≥6 mm
- Evolution or change over time 2
The "ugly duckling" concept is also valuable - benign moles tend to have a similar appearance, whereas an outlier with a different appearance is more likely to be undergoing malignant change 2.
Special Types of Nevi
- Deep penetrating nevus (DPN): A distinct variant of melanocytic nevus that can be misinterpreted as malignant melanoma due to its dark pigmentation and unusual histologic features 4
- Giant congenital pigmented hairy nevus: Associated with increased risk of melanoma and requires long-term follow-up 5
Clinical Management
For typical moles, no specific intervention is required. For atypical moles:
- Prophylactic excision of all atypical nevi is not recommended 6
- Atypical moles with changes suggestive of malignant melanoma should be biopsied using an excisional method 2
- Patients with atypical mole syndrome should have regular total-skin examinations by a physician at least annually 6
Proper diagnosis requires histopathological examination, which should include confirmation of melanocytic nature, assessment of malignancy, and evaluation of architectural features 7.