Melanocytic Nevus - Classification

Classification

Melanocytic nevi represent a family of lesions. The most common variants are:

• Location:
  • Junctional nevus: the nevus cells are located along the junction of the epithelium and the underlying dermis. A junctional nevus is flat and brown to black.
  • Compound nevus: a mixture of junctional and intradermal proliferation. Compound nevi are slightly raised and brown to black. Beauty marks are usually compound nevi of either the acquired variety or congenital variety.
  • Intradermal nevus: the nevus cells are located in the dermis only. Intradermal nevi are raised; most are flesh-colored (not pigmented).
• Dysplastic nevus (nevus of Clark): usually a compound nevus with cellular and architectural dysplasia. Like typical moles, dysplastic nevi can be flat or raised. While they vary in size, dysplastic nevi are typically larger than normal moles and tend to have irregular borders and irregular coloration. Hence, they resemble melanoma, appear worrisome, and are often removed to clarify the diagnosis. Dysplastic nevi are markers of risk when they are numerous (atypical mole syndrome). According to the National Cancer Institute (NIH), doctors believe that, when part of a series or syndrome of multiple moles, dysplastic nevi are more likely than ordinary moles to develop into the most virulent type of skin cancer called melanoma.
• Blue nevus: It is blue in color as its melanocytes are very deep in the skin. The nevus cells are spindle shaped and scattered in deep layers of the dermis. The covering epidermis is normal.
• Spitz nevus: a distinct variant of intradermal nevus, usually in a child. They are raised and reddish (non-pigmented). A pigmented variant, called the 'nevus of Reed', typically appears on the leg of young women.
• Acquired nevus: Any melanocytic nevus that is not a congenital nevus or not present at birth or near birth. This includes junctional, compound and intradermal nevus.
• Congenital nevus: Small to large nevus present at or near time of birth. Small ones have low potential for forming melanomas, however the risk increases with size, as in the giant pigmented nevus.
• Giant pigmented nevus: these large, pigmented, often hairy congenital nevi. They are important because melanoma may occasionally (10 to 15%) appear in them.
• Intramucosal nevus: junctional nevus of the mucosa of the mouth or genital areas. In the mouth, they are found most frequently on the hard palate.
• Nevus of Ito and Nevus of Ota: congenital, flat brownish lesions on the face or shoulder.
• Mongolian spot: congenital large, deep, bluish discoloration on the back of Asian babies.
• Recurrent nevus: Any incompletely removed nevus with residual melanocytes left in the surgical wound. It creates a dilemma for the patient and physician, as these scars cannot be distinguished from a melanoma.