Melanocytes in the dark cell area of human vestibular organs.

By using surgical materials obtained from 7 cases of vestibular schwannoma, the ultrastructure of melanocytes in the dark cell area of human vestibular organs was examined by light microscopy and electron microscopy. Paraffin sections were stained with hematoxylin and eosin. Glutaraldehyde-fixed specimens were observed by electron microscopy. Melanocytes were found in the subepithelial layer of the dark cell area. Melanocytes had round or spindle-shaped nuclei and clear cytoplasm with brown pigment granules which were thought to be melanin granules. Besides melanocytes, there were fibroblasts and small blood vessels. By electron microscopy we found melanocytes with round shaped melanosomes in various stages of pigmentation, well-developed Golgi apparatus and endoplasmic reticulum in the cytoplasm, and many cytoplasmic processes. There were pinocytotic vesicles just under the limiting membrane of the melanocytes, and intermediate filaments were abundant in the cytoplasm. On the other hand long-spacing collagen was found in the connective tissue area around melanocytes.