cytology

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Melanocytes are components of the epidermis. They are ovoid cells with a large number of long dendritic processes. The processes interdigitate with neighbouring keratinocytes and there are regions of close apposition between the two cells.

Poorly shown with conventional stains under the light microscope, the electron microscope more readily identifies melanocytes by the large number of melanin granules - melanosomes - within their cytoplasm. Melanosomes are bound by a lipid bilayer produced by Golgi apparatus and are secreted via the dendritic processes into keratinocytes. The dendrites are used to convey the melanosomes to the surrounding keratinocytes.

The number of melanocytes does not vary between races. The keratinocytes of Negroid races degrade their bigger melanosomes less readily than Caucasian counterparts.

When melanocytes leave they epidermis and enter the dermis they become naevus cells which are rounder, lack dendrites and tend to accumulate together in 'nests'.

Last reviewed 01/2018