Epithelioid blue nevus of the oral mucosa: a rare histologic variant.

Epithelioid blue nevus (EBN) is an extremely rare histologic variant of blue nevus that has only recently been identified. Unlike other variants of blue nevus, which primarily are composed of pigmented, spindle-shaped melanocytes, EBN is characterized by large, well-defined, heavily-pigmented polygonal or epithelioid-shaped melanocytes intermixed with less densely pigmented epithelioid- and fusiform-shaped melanocytes. Furthermore, in contrast to other benign melanocytic proliferations, the lesional cells in EBN exhibit little or no maturation as they extend deeper into the underlying tissue. Blue nevi are the second most common form of nevus in the oral cavity. However, to our knowledge, the epithelioid variant has not been previously identified in the mouth. Only 6 examples of EBN have been identified in the skin of the head and neck. We now report the first documented case of EBN involving the oral mucosa. A brief review of the clinical and histopathologic features of EBN is also presented.