Suprabasal Spread of Melanocytes in Dysplastic Nevi and Melanoma In Situ

Abstract

Multiple criteria on routinely stained sections allow one to make a diagnosis of a dysplastic or "Clark" nevus (CN) versus melanoma in situ (MIS), and one of these is suprabasal spread of melanocytes. The extent of suprabasal spread of melanocytes in otherwise conventional CN and the combination of a sensitive marker of melanocytes combined with Ki-67 to assess the differences between the proliferation of melanocytes at the junction and those above it have not yet been studied. Fifty classic examples of CN and 27 cases of MIS were culled from the files of a university-based dermatopathology practice. All cases were stained with a 2-color method (MART-1/tyrosinase red, Ki-67 brown) to evaluate morphologic and immunohistochemical differences in these lesions. Fifteen of 50 cases of benign CN demonstrated suprabasal spread compared with 27 of 27 cases of MIS. The majority of CNs with suprabasal spread (13 of 15) showed a 0% Ki-67-labeling rate among the suprabasal melanocytes, and the majority of MISs (23 of 27) showed a 20% or greater Ki-67-labeling rate in suprabasal cells. Suprabasal melanocytes can be seen by immunostaining in otherwise unremarkable CN, wherein they are not notable in routinely stained sections, but their proliferation rate is much less than in MIS.

SIRT1 and Ki67 immunohistochemical expression in progression of cutaneous malignant melanoma

“…Melanoma is known to exh ibit aberrant expression of proliferation markers, and these abnormalities are considered important steps in the genesis and progression of melano ma [57].An increasing literature describes the role o f pro liferat ion markers in the evaluation of melanocytic tumors [58]. Ki67 staining has been shown positive in mu ltip le lesions, 5% of positivity on melanocytic cells in most benign nevi, although there have been reports of up to 15% positivity in Spit z and dysplastic nevi [59][60][61][62]. Conversely, Ki67 staining is reported as positive in 13-30% of the cells in a malignant melano ma, although individual cases can show almost 100% nuclear positivity [62,63].…”