Skin mole. Coloured scanning electron micrograph (SEM) of detail from a human skin mole. Moles are common skin lesions. They are correctly called melanocytic naevi, as they are due to a proliferation of the pigment cells, melanocytes. If they are brown or black in colour, they may also be called pigmented naevi. Moles are benign in nature (harmless), but a malignant melanoma (cancerous mole) may arise within a mole. Magnification: x500 when printed 10cm wide.