Common moles (Nevi)
Common moles, which are also known as Acquired Nevomelanocytic Nevi (NMN) are benign acquired growths of the skin. Common moles are composed of clusters of melanocytic (pigment producing) cells and can occur anywhere on the body. They typically appear during childhood, but new moles can continue to appear into adulthood.
NMN are classified based on their location within the skin:
- Junctional: Cells of the nevus or mole arise at the Dermal-Epidermal Junction, typically they are pigmented and flat.
- Compound: Nevus cells found both in intra-epidermal and dermal layers. These moles are pigmented and elevated papules or nodules
- Dermal: All nevus cells are in the dermis, where they lose the capability to produce pigment. Typically these moles are raised and light in color
Dysplastic (Atypical) Nevi
A dysplastic nevus or atypical mole is a special type of acquired mole, where the pigmented producing cells or melanocytes have undergone change. As these cells become more atypical, they develop the risk for being a precursor to melanoma (however the presence of abnormal cells does not mean you are diagnosed with a melanoma or “pre-melanoma”).
Dysplastic Nevi may form in an existing mole that has changed over time or with cumulative sun exposure, or they may arise as a new mole that presents later in life. They have characteristic features that separate them from common moles as they are typically larger, variable in color, asymmetric in outline, and have irregular borders. Any mole that does not follow the ABCDE’s of melanoma should be evaluated by a dermatologist.
Your dermatologist can examine any new or changing moles that may be present to determine if it may need a biopsy. For most people an annual skin exam is recommended to do so, however in those more prone to developing dysplastic nevi or with a family history or Melanoma, a skin check should be performed every 6 months.
Treatment is required following a biopsy of dysplastic nevi, and is done with either a shave or surgical excision, depending on the degree of atypia or change. Dysplastic Nevi range from mildly dysplastic, to moderate or severely dysplastic. Just because a mole becomes dysplastic does not mean it is definitely going to continue progressing into a melanoma, however standard practice is to treat these atypical cells by completely removing them.