Rare tumour of one of the salivary glands in the mouth, usually found in the parotid gland, below and in front of the ears (90 per cent of cases), and very rarely in the glands beneath the jaw or tongue. Tumours of the parotid gland are usually benign, but in rare cases they can become malignant; in the other two glands roughly half the cases are benign. With a tumour of the parotid gland there is swelling directly in front of and/or under the ear; the tumour is painless, and grows steadily. Possible complications include paralysis of one side of the face, facial pain or painful tic, all caused by pressure on a nerve. Malignant tumours are more likely to grow through into the surrounding area and can metastasize. Tumours of the other salivary glands behave in the same way, with swelling on the edge of the lower jaw or the bottom of the mouth. They do not exert pressure on important nerves.