Is melanocyte density our last hope? Comparison of histologic features of photodamaged skin and melanoma in situ after staged surgical excision with concurrent scouting biopsies

Abstract

Differentiating melanocytic hyperplasia (MH) on photodamaged skin from junctional lentiginous melanocytic proliferations (JLMP), early evolving melanoma in situ (MIS), or the periphery of a lesion of MIS on staged excision can be challenging. Although previous cross-sectional studies have elucidated important criteria for distinguishing MH on photodamaged skin from more concerning lesions, this study highlights a technique to treat JLMP and MIS with staged mapped excision and baseline scouting biopsies of adjacent nonlesional photodamaged skin to assist in determination of surgical margin clearance. Additionally, we compare the lesional and photodamaged control biopsies from the same patient to evaluate relevant histologic criteria that may be used to distinguish MH in photodamaged skin from JLMP/MIS, while minimizing confounding factors. There was a statistically significant difference (P ≤ 0.05) found for melanocyte density, irregular melanocyte distribution, melanocyte clustering, follicular infundibulum involvement, and nesting. However, criteria such as nesting, epithelioid cells and melanocyte clustering were seen in both photodamaged skin and MIS. These findings underscore the fact that histologic features of photodamaged skin can overlap with the histopathological features of MIS. Of all of the criteria evaluated, melanocytic density was the most objective histologic criterion and did not show overlap between the sun-damaged and JLMP/MIS groups. K E Y W O R D S atypical junctional melanocytic hyperplasia, lentigo maligna, melanoma in situ, scouting biopsy, slow Mohs, staged excision How to cite this article: Speiser J, Tao J, Champlain A, et al. Is melanocyte density our last hope? Comparison of histologic features of photodamaged skin and melanoma in situ after staged surgical excision with concurrent scouting biopsies.

Staged Excision of Lentigo Maligna of the Head and Neck: Assessing Surgical Excision Margins With Melan A, SOX10, and PRAME Immunohistochemistry

“…SOX-10, a transcription factor involved in the differentiation of progenitor cells into melanocytes, is a nuclear marker that avoids the mentioned pitfalls involved with Melan A. 17,23,25,43 SOX10 has been demonstrated to be both a specific and a sensitive IHC stain for melanocytes when diagnosing melanoma and improved the diagnostic accuracy for LM when assessing surgical excision margins in our cohort 23 (Fig. 2B).…”

“…It is well established that Melan A may overestimate melanocyte density and falsely stain pseudo-melanocytic nests and, therefore, may result in the overdiagnosis of LM on surgical excision margins. 17–23…”

“…It is well established that Melan A may overestimate melanocyte density and falsely stain pseudo-melanocytic nests and, therefore, may result in the overdiagnosis of LM on surgical excision margins. [17][18][19][20][21][22][23] Melanin is synthesized within melanosomes in melanocytes, which are located within the basal layer of the epidermis and the hair bulb. Melanin is transferred from melanocytes to keratinocytes, where they accumulate perinuclearly to form a protective layer above the nucleus.…”

“…21–25 MITF and SOX10 highlight the nuclei of melanocytes and are more accurate in assessing cellularity and nuclear morphology of melanocytes and, therefore, may improve the diagnosis of LM. 17,23,25,26…”

“…Unfortunately, the reliability of these criteria remains unproven. [14][15][16][17] Immunohistochemical (IHC) stains such as Melan A, HMB45, MITF1, and SOX10 have been used to diagnose LM by identifying melanocytes within the epidermis. Melan A is the most widely used marker of melanocytes and targets cytoplasmic antigens within melanocytes.…”