When a mole hurts when you itch it does that mean it's cancerous?

Concerning. Moles that start to itch, scab, or bleed should be brought to the attention of your friendly dermatologist.
Possibly. Changes in a mole such as color, shape, size, texture may be a sign of malignant transformation. If the mole feels different such as being painful or itchy or if it's bleeding are all reasons to get it seen by a dermatologist and possible biopsy to make sure it's not becoming a melanoma.