This 44-year-old man presented to his GP with a nodule on the left side of his hard palate. His dentist had noticed it around two years previously and had referred him to a dental hospital – but he had not kept the appointment or seen his dentist since. The nodule had grown slowly since and his wife had finally seen it and urged him to seek medical attention. So he now presented in a state of great agitation.
Examination showed a firm, painless swelling just over 1.5cm in diameter. It was well demarcated, pinkish and the overlying mucosa was intact. There was no evidence of regional lymphadenopathy and no history of oral trauma. His past medical history was unremarkable.
He was referred for investigation of the lesion, and a CT scan showed a smooth, well-marginated tumour. A biopsy revealed a benign tumour characteristic of a pleomorphic adenoma.
The entire tumour was excised with a wide margin and there has been no recurrence at 12 months' follow-up.
The problem
- Pleomorphic adenoma is a benign tumour of the salivary gland and is the most common salivary gland tumour in all ages.1
- It makes up 45-75% of all salivary gland neoplasms and the annual incidence is approximately two to 3.5 cases per 100,000 population.2,3
- The average age at presentation is between 43 and 46 years.
- Tumours affecting salivary glands may be benign or malignant and are diverse in their pathology.
- The major salivary glands are the parotid glands, submandibular glands and sublingual glands, but there are also up to 1,000 minor salivary glands.
- Some 80% of salivary gland neoplasms arise in the parotid glands, 10-15% in the submandibular glands and the remainder in the sublingual and minor salivary glands
- About 80% of parotid neoplasms are benign, but the relative proportion of malignancy increases in smaller glands. About half of submandibular gland neoplasms and most sublingual and minor salivary gland tumours are malignant.
- A pleomorphic adenoma developing in a minor salivary gland such as this is rare.
Features
- Pleomorphic adenoma is usually solitary and presents as a slow-growing, painless, firm, single nodular mass.
- Most develop in the parotid gland (see above), where they are usually mobile and can cause atrophy of the mandibular ramus. The example here developed in the hard palate and was immobile.
- Patients with minor salivary gland tumours may present with a variety of symptoms depending on the site – including dysphagia, hoarseness, difficulty chewing and epistaxis.
- Pleomorphic adenomas – though classified as benign – can become huge and may undergo malignant transformation, causing signs of facial nerve weakness.
- Features of a salivary gland mass suggesting malignancy include:
– hardness
– fixation
– tenderness
– infiltration of surrounding structures ulceration.
Diagnosis
- Differential diagnosis includes:
– Warthin's tumour – a benign parotid tumour typically seen in 60- to 70-year-olds
– salivary gland malignancies – see below.
- Salivary gland tumours are usually diagnosed using both biopsy and imaging.
- Core-needle biopsy is more accurate than fine needle aspiration biopsy and allows histological typing.
- Both MRI and CT scanning can be used, but CT allows direct, bilateral visualisation of the tumour and can better assess surrounding tissue invasion in malignancies.
Management
- Surgical resection is the mainstay of treatment for any salivary gland tumour.
- Benign tumours of the parotid gland are treated with superficial or total parotidectomy.
- The latter is more common for pleomorphic adenomas because of the high incidence of recurrence.
- Benign tumours of the submandibular and minor salivary glands are treated with simple excision.
Dr Raj Singh is a ENT GPSI in Manchester
References
1 Eveson J, Kusafuka K, Stenman G and Nagao T. Tumours of the salivary glands. In: Barnes L, Eveson JW, Reichart P, Sidransky D, eds. Pathology and Genetics of Head and Neck Tumors. IARC Press, France. 2007:254-8
2 Pinkston JA and Cole P. Incidence rates of salivary gland tumours: results from a population-based study. Otolaryngol Head Neck Surg 1999;120:834-40
3 Spiro RH. Salivary neoplasms: overview of a 35-year experience with 2,807 patients. Head Neck Surg 1986;8:177-84
