How are canker sore and what oral cancer differ?

Oral Ca: Both are ulcerations in the oral cavity, but there are significant differences. Canker sores are usually in the cheeks and lips, oral ca can be anywhere in the oral cavity. Canker sores are almost always painful, while oral ca ulcerations usually aren't painful. The biggest difference is canker sores will heal in 2 weeks, occasionally up to a month, and oral ca ulcerations don't heal, ever.

Totally different: Totally different in terms of causation and clinical course. Canker sores gone in 7-10 days. Any ulcer persisting longer than this should be assessed by oral surgeon or ENT doc.