I have an itchy mole on my back, is it cancerous?

Get it checked! We can't know, but one thing for sure is that if you have a changing lesion on your skin, you must get it check out with a pcp, dermatologist or other physician with interest in skin diseases/disorders. Please? Get it checked.
Unknown. Various skin lesions can appear to be "moles". Cancerous features of true moles include size over 6 mm, irregular pigment, irregular borders or recent change in any of these features. "itchy mole" on the back could be benign tumor, inflammation/drug/infection/allergy related pigment or possibly cancer. Seek medical advise for definitive diagnosis.