Benign melanocytic tumors (melanocytic nevi) and malignant tumors (malignant melanoma, melanoma, melanoblastoma) are tumors of melanocytes, cells of neuroectodermal origin. These cells enter the epidermal basal layer during embryonal development. Later produce melanin, brown pigment, which is taken up by surrounding melanocytes. Melanin stains the epidermis brown and protects the body against UV radiation.

In normal skin the melanocytes are regularly dispersed within the basal layer of the epidermis. Their cytoplasm is pale and nuclei have fine chromatin.

For details concerning pathology of melanocytic lesions refer to the specialized literature.