Moles or nevi are harmless pigmented skin spots and tumors on the skin surface. They are built up by MELANOCYTES, which have aggregated at the so-called "rete ridges" of the EPIDERMIS and thus become visible. MELANOCYTES singularly scattered in the basal layer of the EPIDERMIS are invisible with the naked eye, but if they have proliferated (increased in number) and clustered (aggregated), they can be seen as pigmented skin lesions.

MELANOCYTIC MOLES or NEVI often appear in high numbers on almost everyone's skin. Given their high numbers in a worldwide population, the event malignifying (turning malignant and deloping melanoma) is extremely rare. So, they can not be considered precursors of melanoma.

On the other hand, in the early development stage, malignant melanoma may mimick a melanocytic mole or nevus, since melanocytic nevi share plenty of shape features of malignant melanoma. Therefore, early melanomas may be overlooked and diagnosed too late, if they have effectively disguised under the visual aspect of a harmless mole. As a consequence, regular performing self-exams of the skin will help to build a personal visual expertise on one own's moles.

What makes the visual assessment of melanocytic moles or nevi troublesome is the fact that they often look alike and yet quite different from each other. So, visual training and expertise is required to build a safe baseline knowledge of looking at moles.

The image examples displayed above show a melanocytic compound nevus (left) and a dysplastic nevus (right). Both findings are benign. They do, however, exhibit some suspicion criteria of the ABCD rule (border irregularity) and thus require close monitoring over time (size and aspect changes?). If any change would happen, biopsy clarification would be required.