There is little evidence to guide surgical management of biopsies yielding the histologic descriptor atypical intraepidermal melanocytic proliferation (AIMP).

Determine frequency of and factors associated with melanoma and melanoma in-situ (MIS) diagnoses after excision of AIMP and evaluate margins used to completely excise AIMP.

Retrospective, cross-sectional study of 1127 biopsies reported as AIMP and subsequently excised within one academic institution.

Melanoma (in situ, stage 1A) was diagnosed after excision in 8.2% (92/1127) of AIMP samples. Characteristics associated with melanoma/MIS diagnosis included age 60-79 years (odds ratio [OR] 8.1, 95% confidence interval [CI] 2.5-26.2), age ≥80 years (OR 7.2, 95% CI 1.7-31.5), head/neck location (OR 4.9, 95% CI 3.1-7.7), clinical lesion partially biopsied (OR 11.0, 95% CI 6.7-18.1), and lesion extending to deep biopsy margin (OR 15.1, 95% CI 1.7-136.0). Average ± standard deviation surgical margin used to excise AIMP lesions was 4.5 ± 1.8 mm.

Single-site, retrospective, observational study; interobserver variability across dermatopathologists.

Dermatologists and pathologists can endeavor to avoid ambiguous melanocytic designations whenever possible through excisional biopsy technique, interdisciplinary communication, and ancillary studies. In the event of AIMP biopsy, physicians should consider the term a histologic description rather than a diagnosis, and, during surgical planning, use clinicopathologic correlation while bearing in mind factors that might predict true melanoma/MIS.