CD99 expression in Merkel cell carcinoma: a case series with an unusual paranuclear dot‐like staining pattern

BACKGROUND: Merkel cell carcinoma (MCC) is a rare neuroendocrine cancer of the skin. The utility of CD99 (MIC-2) in the diagnosis of MCC has been previously studied, with reported rates of expression ranging from 13 to 55%. When specified, a membranous or cytoplasmic staining pattern was considered significant. Recent studies of CD99 have identified a paranuclear dot-like expression pattern in certain non-neuroendocrine pancreatic and colonic …