clinical features distinguishing atypical from benign nevi

Clinical manifestations: Color 1) benign nevi: uniform tan or brown 2) atypical nevi: a) variable mixtures of tan, brown, black or red/pink within a single nevus b) nevi may look very different from each other Shape 1) benign nevi: a) round b) sharp, clear-cut borders between the nevus & the surrounding skin c) may be flat or elevated 2) atypical nevi: a) irregular borders b) pigment may fade off into surrounding skin c) macular portion at the edge of the nevus Size 1) benign nevi: generally < 6 mm in diameter 2) atypical nevi: a) generally > 6 mm in diameter b) may be > 10 mm in diameter c) occasionally < 6 mm in diameter Number 1) benign nevi: a) in a typical adult, 10-40 nevi are scattered over the body b) 15% of individuals have no nevi 2) atypical nevi: a) often > 100 nevi b) occasionally, may be only one nevus Location 1) benign nevi: a) generally on sun-exposed surfaces of the skin, above the waist b) scalp, breasts & buttocks are rarely involved 2) atypical nevi: a) sun-exposed areas b) the back is the most common site c) dysplastic nevi may also be seen on the scalp, breasts & buttocks

References

Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 545