Neuroendocrine Skin Carcinoma Coexpressing Cytokeratin and Neurofilament Proteins

Abstract

Neuroendocrine (Merkel cell) carcinomas of the skin have been recognized as such for several years.^1,9 Given the reported wide variability in the morphology and clinical evolution of these tumors, the notion that may they comprise several variants rather than a single type has been advocated.^2,9 Electron microscopy has played a key role in the early recognition of these tumors^1,9 while immunohistochemical studies for various neuroendocrine markers have facilitated their subsequent diagnosis and improved our understanding as to their complexity by the demonstration of immunoreactivity for NSE (neuron specific enolase) and a number of neuro-peptides.^4,8,9

There has also been considerable interest in the study of the cytoskeletal intermediate filament complement of neuroendocrine neoplasms in general and of those of the skin in particular. Early reports indicated that neuroendocrine skin carcinomas had neurofilaments¹⁰ while subsequent investigations determined that they had cytokeratin.¹¹ However, more recent studies have indicated that at least some neuroendocrine skin carcinomas could in fact coexpress both aforementioned classes of intermediate filament proteins.^12,13 This brief report is presented to confirm the latter investigations.