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Original Investigation
November 2016

Prevalence and Gross Morphologic Features of Perianal Melanocytic Nevi

Author Affiliations
  • 1Rush Medical College, Rush University, Chicago, Illinois
  • 2Department of Dermatology, Rush University Medical Center, Chicago, Illinois
JAMA Dermatol. 2016;152(11):1209-1217. doi:10.1001/jamadermatol.2016.1885
Key Points

Question  How common are perianal melanocytic nevi?

Findings  In a prevalence study of 236 adults attending 1 dermatologist’s practice, perianal nevi of any size were evident in nearly half of patients. In whites, presence of at least 1 perianal nevus was significantly associated with history of any atypical nevi removed, atypical nevus pattern, and at least 1 extant atypical nevus anywhere on the skin.

Meaning  Perianal nevi may be associated with significant melanoma risk factors, and consideration should be given to examination of the perianal area during melanoma screening and surveillance.

Abstract

Importance  The presence of numerous melanocytic nevi is a significant melanoma risk factor, but there are scant data related to prevalence and morphologic features of melanocytic nevi in the perianal area. The prognosis of perianal melanoma is often dismal because of hidden location and diagnosis delay.

Objective  To determine prevalence and morphologic features of perianal melanocytic nevi.

Design, Setting, and Participants  This study was conducted for 11 months during 2013 and 2014 at an outpatient dermatology clinic in Chicago, Illinois, with a convenience sample of 236 adults (men and women of all races, ≥18 years) presenting to 1 dermatologist for melanoma and/or skin cancer screening or surveillance. The analysis was conducted during April through July 2015.

Main Outcomes and Measures  Prevalence and morphologic features of perianal nevi according to race/ethnicity, sex, and age.

Results  Of 236 participating patients, 219 were non-Hispanic white; 4, Hispanic white; and 13, nonwhite. Patients included 138 men and 98 women, ages 23 to 84 years (median age, 55 years; mean [SD], 53 [15] years). Perianal nevi of any size, at least 2 mm in diameter, and at least 5 mm in diameter were evident in 48.9% (107 of 219), 39.7% (87 of 219), and 5.5% (12 of 219) of non-Hispanic whites, respectively; 50.0% (2 of 4), 0 (0 of 4), and 0 (0 of 4) of Hispanic whites, respectively; and 38.5% (5 of 13), 38.5% (5 of 13), and 0 (0 of 13) of nonwhites, respectively. In non-Hispanic whites, the presence of at least 1 perianal nevus was significantly associated with history of atypical nevus excision (odds ratio [OR], 2.9; 95% CI, 1.5-5.7); and extant findings of at least 1 atypical nevus (OR, 2.2; 95% CI, 1.3-3.9); atypical nevus pattern (≥20 nevi that were ≥2 mm in diameter), plus at least 5 nevi that were 5 mm or greater in diameter (OR, 1.8; 95% CI, 1.1-3.1); and at least 4 atypical nevi 5 mm or greater in diameter (OR, 1.9; 95% CI, 1.1-3.3).

Conclusions and Relevance  In this study, perianal melanocytic nevi were common and were associated with prominent and atypical nevi elsewhere. The perianal area is worthy of attention during melanoma screening and surveillance.

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