Reflectance confocal microscopic visualization of melanocytic bodies in the stratum corneum overlying acral lentiginous melanoma

Abstract

Background: We present a case of RCM evaluation of ALM surgical margins demonstrating intracorneal melanocytic bodies overlying subsequently confirmed melanoma in situ by histopathology. Case Presentation: A 73-year-old male with a history of acral lentiginous melanoma (ALM) of the right great toe presented to our clinic for evaluation of positive surgical margins. The positive margin was localized for examination and subsequent biopsy with reflectance confocal microscopy (RCM) which allowed targeted reresection of the area of concern. Three punch biopsies were obtained in the area of concern, which confirmed residual melanoma in situ. Immunostains confirmed the cellular remnants in the stratum corneum were melanocytic. To correlate the intra stratum corneum findings seen with confocal to the histopathology, a 3D rendering of a stack of images was used to demonstrate the location. Discussion: Typically, acral surfaces are challenging to examine with RCM due to the limited ability of light to penetrate thickened stratum corneum; however, we observed unique cellular features with confocal. Scattered hyper-reflective pleomorphic cells consistent with melanocytes were observed in the stratum corneum, although the visualized underlying epidermis appeared normal. Confocal microscopy may aid in diagnosis and management of ALM, especially in the context of positive surgical margins.

Concordance between reflectance confocal microscopy and histopathology for the diagnosis of acral lentiginous melanoma

“…In this study, RCM detected uneven highly refractive granules in the epidermis, a significant diagnostic clue for ALM, in 18 cases (66.7%). Natarelli et al 12 . detected highly refractive pleomorphic cells, which were considered to be melanocytes, scattered in the stratum corneum at the positive edge of ALM by RCM, although the underlying epidermis appeared normal.…”

“…Natarelli et al. 12 detected highly refractive pleomorphic cells, which were considered to be melanocytes, scattered in the stratum corneum at the positive edge of ALM by RCM, although the underlying epidermis appeared normal. This feature was also observed in three cases in the present study.…”

Management of acral lentiginous melanoma: current updates and future directions

“…However, given the high frequency of preoperative biopsy under-staging ALM lesions, wider margins and sentinel lymph node biopsy may be considered in patients with lower stage ALM but with residual pigmentation on exam ( 26 ). Reflectance confocal microscopy can be useful in the setting of positive margins, as it assists with targeted resection of the area of concern ( 32 ).…”