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.

The atypical mole is a special kind of dysplastic melanocytic nevus, with clinical and microscopic features suggestive of an intermediate form between the common acquired mole and melanoma. Atypical skin moles are important markers for both familial and non familial melanoma. As many as 50% of patients with “sporadic” melanoma have been observed to have atypical skin moles. The incidence of atypical skin moles in the general population has been estimated to be 1.8% to 10% and possibly as high as 19%. The presence of atypical skin moles has been established as an independent risk factor for melanoma, along with several other cutaneous traits, including red or blonde hair, solar lentigines, skin type 1 or 2, and increased numbers of common acquired melanocytic nevi. One study found the adjusted relative risk of melanoma to be 2 for a single atypical mole and 12 for 10 or more atypical skin moles. Another found a relative risk of 1.6 when one to four atypical skin moles were counted and 6.1 for five or more atypical skin moles. The risk ofmelanoma attributable to atypical skin moles may be further exacerbated by the coexistence of other melanoma risk factors, such as skin type 1 or 2. The increased risk for melanoma is particularly true in the setting of the atypical mole syndrome (AMS). AMS encompasses individuals with multiple atypical skin moles arising sporadically or in a setting of a family history of atypical skin moles or melanoma. AMS has been divided into a number of forms. Type A is sporadic atypical mole without melanoma; type B is familial atypical mole without melanoma; type C is sporadic atypical mole with a personal history of melanoma; type D-l is familial atypical mole with one family member with melanoma; and type D-2 is familial atypical mole with two or more family members with melanoma. Meticulous screening of family members may demonstrate that presumptive cases of sporadic AMS are actually familial. All patients with AMS have an increased risk for developing melanoma, although the magnitude of the risk varies among the AMS types. The relative risk of melanoma is least in patients with AMS types A and B, and has been estimated to be 7 with a cumulative lifetime risk of 6%. The relative risk of melanoma in type D-2 patients may be as high as 1000 or greater compared with the general population. Individuals with AMS also appear to be at an increased risk for multiple primary cutaneous melanomas.One study found a 35.5% cumulative 10-year risk of developing a second melanoma in those with AMS and a history of melanoma as compared with a 17% 10-year risk of developing a second melanoma in those with a history of melanoma but without AMS. Patients with AMS may also be at increased risk of conjunctival and intraocular melanoma. The recognition of AMS may allow early detection of melanoma and identification of those at risk and provide the opportunity for the initiation of preventive measures. A great deal of discussion has centered on the validity of the atypical mole as a distinct entity and its potential for progression to melanoma. Much disagreement over its nature stems from a lack of uniform clinical and microscopic criteria to define it. Atypical skin moles generally demonstrate both clinical and microscopic evidence of distorted and disordered architecture.