Benign parotid tumours

All surgical disciplines have moved towards subspecialisation with the development of less invasive procedures and reduction in surgical morbidity. The difficulty with salivary tumours is that they are rare and have a long clinical course that requires follow up data for a decade or more. Prospective randomised trials have therefore not been undertaken, and progress happens slowly, with new generations of surgeons building on the experience of their peers.

Improved methods of assessment (magnetic resonance imaging, computed tomography, ultrasound, and fine needle aspiration biopsy) have had a major impact on salivary gland surgery because of increased confidence in distinguishing benign from malignant tumours. Of discrete lumps, only 5% will prove to be malignant, and over half of these can be recognised on clinical examination alone.¹ The addition of modern techniques for investigation reduces further the risk of inadvertently encountering a malignant neoplasm. This then avoids the traditional “one approach fits all” attitude to parotid surgery.

Most benign parotid tumours are either pleomorphic adenomas (71%) or Warthin's tumours (22%).² Unfortunately pleomorphic adenoma has a reputation for recurrence that has lingered since the 1940s and 50s. The nature of pleomorphic adenoma was then unclear for, as its name implies, it has a variable appearance and so was thought to be a hamartoma rather than a neoplasm. Treatment was by crude enucleation, and in some centres the tumour capsule was even left in situ, with obvious consequences. The reputation of the tumour for recurrence was given further credence in 1958 by Patey and Thackray's work,³ which showed an incomplete capsule through which small buds of tumour protruded. This was the rationale for the traditional superficial parotidectomy. The technique was promoted by Hamilton Bailey and others as a solution to the recurrence problem, which it proved to be. Superficial parotidectomy was adopted universally as the treatment of choice for the discrete parotid lump.

During the early years of debate, through serendipity, Alan Nicholson, a surgeon at the Christie Hospital in Manchester, held a different view. He felt that recurrence was due to inadequate surgical exposure, which leads to rough handling and rupture of the tumour rather than the biological nature of the tumour itself. At this time, parotid tumours were managed under local anaesthesia by an incision made directly over the tumour. In contrast he used wide exposure through a pre-auricular skin flap but then proceeded to a local dissection of the tumour rather than a parotidectomy. By the time the debate was resolved in favour of superficial parotidectomy he had 10 years of data, which showed no increase in the risk of recurrence by the less invasive method, and so he and his successors, Gleave and Hancock, persisted with the technique in isolation from the surgical community.

The recent analysis of this experience, under-pinned by a mean follow up period of 15 years, shows conclusively that local dissection of benign parotid tumours is a safe procedure with recurrence rates of 2%—no more than that with traditional parotidectomy.⁴ The advantage is that minimal surgery produced less morbidity as measured by nerve injury, Frey's syndrome (a disorder characterised by excessive gustatory sweating of the skin overlying the parotid), and the formation of neuromas.⁵ Neither does it cause a deformity of the cheek due to loss of parotid tissue. The Christie data show that 70% of patients with discrete parotid lumps could safely avoid formal parotidectomy.

Surgeons are traditionalists, and the early experience of our peers has coloured current surgical opinion and slowed the introduction of conservative surgery for the benign parotid lump. This situation is now changing, and centres with experience of treating parotid tumours increasingly recognise that benign tumours can be removed safely by techniques much less invasive than a formal parotidectomy.^6-8