Skin Moles

Atypical moles are also called Dysplastic nevi. The atypical mole is a skin mole with irregular border, larger size, and has a collection of distinctive histological features.
Prevalence: 2–8% of whites have atypical moles. They begin developing during puberty and continue to appear throughout life. Atypical moles may be sporadic or have autosomal dominant inheritance (atypical mole syndrome).
Development: Hormones and sun exposure appear to be the major causative factors.
On examination: atypical moles and early malignant melanomas can be identified by the ABCDE rule; the criteria are most pronounced in malignant melanoma.
– Asymmetry.
– Border: irregular.
– Color: multiple colors.
– Diameter: more than 6mm.
– Elevating or Enlarging: a papule mole is usually harmless; a flat mole that grows or develops a nodular component is suspicious.
Atypical moles may have a “fried egg” appearance: broad flat moles (white of egg) with raised central portion (egg yolk). Sporadic atypical moles are commonly found on the palms, soles, breast, umbilicus, genital, and perianal regions.
Histopathology: The histological features of atypical moles are highly controversial. They include: Junctional proliferation of melanocytes extending beyond the dermal component of the mole (shoulder effect) often with fusion of adjacent aggregates (bridging). Melanocytes in aggregates are often spindle-shaped. Fibrosis around the aggregates (lamellar fibrosis). Lymphocytic infiltrates. Atypia of melanocytes: most controversial point; some groups say no atypia; others grade the degree of atypia (mild, moderate, severe).
NB: Many studies have shown that these criteria, greatly simplified here, are not reproducible, even between expert observers, or even by the same observer over a period of time. Almost every flat mole shows some of these features under the microscope.
Similar conditions: Common mole, malignant melanoma.
Treatment: If a patient has only one or a small number of atypical moles, excision is the simplest approach.