ABSTRACT

Also known as a mixed cell tumour it arises from intercalated duct cells and myoepithelial cells. It is the commonest tumour of major salivary glands and in the parotid gland, it forms 90% of all benign tumours; in the submandibular gland, 50%. The average age at presentation is 40-50 years. It is usually unilateral but a few bilateral tumours have been described. The sex incidence is roughly equal. About one-quarter of patients with this tumour have vague local discomfort, but it is usually symptomless apart from the lump, and the facial nerve is never paralysed as the tumour is benign. Most of these tumours occur in the tail of the parotid gland. They can also occur in the retromandibular portion of the parotid gland, either as solitary deep-lobe tumours or dumb-bell tumours. They are very rare elsewhere in the parotid gland. On palpation, the tumour is usually smooth, superficial, round and mobile. The capsule is of compressed normal parotid tissue and varies in thickness. Microscopically duct formation, squamous metaplasia, keratin production and fibroblasts, cartilage, bone precursors may all be found. The tumour is highly implantable and the recurrence rate after primary surgery is about 5%. If simple enucleation is performed, the recurrence rate is between 20 and 30%.