Definition: A nevus (commonly known as a mole) is a small skin lesion, often pigmented in nature, that can appear anywhere on the skin. It can be congenital (present at birth) or acquired later in life. Most nevi are benign, but some can develop into melanoma, a form of skin cancer.

Classification: Nevi can be classified according to their histological location and clinical appearance:

  • Junctional nevi: located at the interface between the epidermis and dermis.
  • Compound nevi: present in both the epidermis and dermis.
  • Intradermal nevi: located exclusively in the dermis.

Appearance and Morphology: Most nevi are tan to black in color, but they can also be red, pink, blue, or colorless. They can be flat or raised, smooth or wrinkled, and with or without hair. The diameter can vary, but usually does not exceed 6 millimeters.

Etiology: The origin of a nevus is linked to the accumulation of melanocytes, the cells responsible for the production of pigment (melanin) in the skin. Genetic factors, sun exposure and hormones can influence the formation and appearance of moles.

Treatment and Removal: Mole removal is often done for cosmetic reasons or if there is a suspicion of malignancy. Biopsy, which involves the surgical removal of part or all of a nevus, is the standard technique for determining whether a nevus is malignant. If a nevus becomes painful, itchy, bleeding, or changes its appearance rapidly, it is essential to see a dermatologist.

Prevention and Monitoring: It is important to monitor nevi regularly to notice any changes. A common technique is the ABCDE rule:

  • A for Asymmetry
  • B for Irregular Edges
  • C for Uneven Color
  • D for diameter greater than 6 mm
  • E for Evolution or change.