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Research Letter
April 2018

Comparison of Melanocyte Density Counts in Topical Imiquimod-Treated Skin Surrounding Lentigo Maligna vs Control Biopsy Specimens

Author Affiliations
  • 1University of Utah School of Medicine, Huntsman Cancer Institute, Salt Lake City, Utah
JAMA Dermatol. 2018;154(4):482-484. doi:10.1001/jamadermatol.2017.5632

Lentigo maligna (LM) is the most common subtype of melanoma in situ, usually occurring in the head and neck regions.1 Several treatment approaches include wide local excisions, staged excisions (confirmation of negative histologic margins prior to surgical reconstruction), radiotherapy, or topical imiquimod 5% cream. The distinction between the surgical border of LM and surrounding background melanocytic hyperplasia common to chronically sun-exposed skin can be ambiguous. Of all the histologic features of LM, only melanocyte density counts (MDC) are statistically significant in making a distinction between LM and background melanocytic hyperplasia.2,3 In 1 study,2 the mean (SD) MDC for the negative control group was 25.6 (9.3) compared with 82.7 (29.3) cells per 400 × magnification for LM. The average margin requirement for LM removal is reportedly 7.2 mm.4 When used in the neoadjuvant setting, topical imiquimod 5% cream enables the removal of most LM tumors with 2-mm margins.5 Gautschi et al6 reported that the risk for local recurrence after topical imiquimod treatment correlates with the total number of melanocytes per millimeter in the original biopsy specimen. We sought to evaluate MDCs in imiquimod-treated LM and negative control biopsy specimens to determine if there was a measurable difference in melanocyte density.