Skin mole. Light micrograph of a section through a junctional or junction naevus, a type of skin mole. This pigmented naevus is produced by abnormal clustering of pigment cells (melanocytes) in the skin at the dermoepidermal junction, where the dermis and epidermis layers meet. At top are loose cornified layers on the surface of the skin. The epidermis is immediately below this, followed by the dermis. Throughout this region there are clusters of melanocyte pigment cells with dark purple nuclei. These dermal pigment cells form the junctional naevus. Like other moles, naevi are harmless, but on rare occasions can become cancerous.