Pleomorphic adenomas

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Pleomorphic adenoma is a benign tumour that affects the major salivary glands, in particular the parotid gland (85% of cases) and the submandibular gland (5% of cases), but also the minor salivary glands (10% of cases). Salivary glands tumours are a quite infrequent pathology, which represent less than 3% of head and neck tumours.

Pleomorphic adenoma, which appears in most cases as a unilateral lesion, is characterised by epithelial cells and myoepithelial cells immersed in a myxoid, mucoid or chondroid stroma. It is surrounded by a fibrous capsule of variable thickness whose integrity must be kept during surgical treatment. This neoplasm is also known as a mixed tumour, since it shows both gland-like and connective-like histological features.

It accounts for 80% of parotid tumours and most commonly affects women, with a peak incidence at around 30-40 years old. This type of tumour usually occurs in the form of a hard nodule and grows slowly, although sometimes it suddenly increases in volume. It can reach considerable dimensions, causing displacements and strains of the branches of the facial nerve. 

Although it is classified as benign, a pleomorphic adenoma can undergo a malignant transformation, with a tendency to recur. In 5% of cases, in fact, if it is not surgically removed, a pleomorphic adenoma can degenerate into a carcinoma (taking the name of Carcinoma ex Pleomorphic Adenoma). This possibility increases in a similar way to the duration of the tumour and the age of the patient.

Causes of Pleomorphic Adenomas

The causes of pleomorphic adenomas are still unknown and the risk factors have not been fully ascertained yet.

In addition to age, risk factors may be related to smoking habits, alcohol abuse, a diet rich in cholesterol and previous radiation therapy treatments in the face and neck regions.

Symptoms of Pleomorphic Adenomas

Pleomorphic adenoma is usually asymptomatic, except for the tendency to grow to reach significant dimensions. This the reason why symptoms usually depend on the volume reached by the mass and on the structures which are consequently compressed.

Therefore, some of the following symptoms can be seen:

• Alteration of the skin profile
• VII cranial nerve neuralgia
• Hearing impairments
• Masticatory impairment
• Swallowing disorders
• Paresis

Diagnosis of Pleomorphic Adenomas

After palpating the area, the physician can prescribe a series of tests aimed at discovering the nature of the lump. In particular:

• Ultrasound scan
• Computed tomography (CT)
• Nuclear magnetic resonance (NMR)
• Biopsy
• Needle aspiration

After carrying out the necessary tests, the physician can diagnose the pleomorphic adenoma.

Treatment of Pleomorphic Adenomas

The treatment of this lesion is always aimed at ensuring the complete removal of the mass (in order to avoid the possibility of recurrence) and at preserving the nearby anatomical structure, thus guaranteeing the patient the best aesthetics and functional results.

The treatment of choice for pleomorphic adenomas is surgery, although there is the risk of damaging the nerve and causing a facial paresis. For surgically non resectable tumours, radiation therapy is widely used, which is also an effective adjuvant therapy.