Pigmented myomatous neurocristoma of the uterus.

A tumor of the myometrium composed of pigmented and nonpigmented melanocytes in a matrix of altered smooth-muscle cells is reported. Electron microscopy and immunohistochemical studies were used to identify the cellular constituents. The neurocristic components were arranged in patterns comparable with those in cellular blue nevus of the skin. Problems relating to histogenesis and to taxonomy are addressed using neurocristic dysplasias of the skin as models. It is believed that melanin production should not be the only criterion used to classify pigmented neurocristic dysplasias arising in extracutaneous mesenchyme. The designation pigmented myomatous neurocristoma is proposed as a suitable alternative to cellular blue nevus To our knowledge, no similar lesion has been reported previously.