Blue nevus of the maxillary sinus. An immunohistochemical and electron microscopic study.

We studied a case of blue nevus of the maxillary sinus by immunocytochemical and electron microscopic techniques. Blue nevus has not been reported previously to occur in the maxillary sinus. The melanocytic nature of this lesion was established based upon the ultrastructural demonstration of pre- and melanosomes, and the presence of S100 protein immunoreactivity in the pigmented cells. Histogenetic aspects of the blue nevus of the maxillary sinus are discussed and an origin in multipotential undifferentiated cells is postulated.