Immune response against antigenically altered melanocytes in the process of tumor progression

Cell-mediated and/or humoral response against nonspecifically altered melanocytes (e.g. physical, chemical)

Autoimmune response against antigens which cross-react with melanocytic nevus cells

Small, symmetrical, well-circumscribed

Junctional, compound, or intradermal nevus

Dense mononuclear cell infiltrate obscures melanocytes

Maturation of melanocytes present

Apoptosis of melanocytic nevus cells

Minimal to moderate cytologic atypia

Few mitoses

Melanin absent in surrounding epidermis