How often do irregular moles turn into melanoma?

Moles and Melanoma: Moles that have asymmetry, border irregularity, color changes or that increase in size should be evaluated to rule out melanoma. Visual inspection is not completely accurate and must often be supplemented with a biopsy to make a proper diagnosis.

It depends: If they are dysplastic or not. Irregularity can refer to appearance or histology. Too broad a q to answer.