Keloids are known to be itchy Pus, swelling and itching in an old keloid might suggest an infection Though cancer can develop in a keloid or any scar for that matter it appears as a chronic non healing ulcer with irregular edges and surface. This is called marjolins ulcer and is a type of squamous cell carcinoma However from the history you have provided it doesn't appear to be cancerous to me. Kindly attach a photo so that a better opinion can be given based on its inspection I hope this answers your question