Close-up of the mouth of a Thai woman, showing her teeth stained from chewing Betel. In Southeast & Central Asia, cigarette smoking is largely replaced by the chewing of tobacco, betel nut or leaf and lime (calcium hydroxide). Betel is the leaf of the betel-pepper (Piper betle). Cancers of the tongue, mouth & pharnyx are common in these areas & studies have shown that the sites of tumours are related to the position in the mouth where the chewed quid is held. In some parts of Asia such oral cancers account for 20% of all cancers reported.