Developmental disorders (Table 42.1)

Aplasia/agenesis

Congenital absence of one or more of the major salivary glands can occur but is very rare. When it does it is usually the parotid gland that is affected.

Duct atresia

Again this disorder is extremely rare. Usually the submandibular duct in the floor of the mouth fails to canulate during embryological development. The newborn infant presents within 2 or 3 days of life with submandibular swelling on the affected side due to a retention cyst in the submandibular salivary gland.

Congenital fistula

Patients with branchial cleft anomalies present usually with unilateral painless swellings in the region of the parotid. Rarely they are bilateral. They form sinus tracts either in the crease behind the pinna or in front of the tragus. They discharge saliva intermittently. Abscess formation due to secondary infection may occur. Complete surgical excision of the sinus tract is essential. The dissection is often very extensive and full dissection of the facial nerve may be required.

Ectopic and aberrant salivary tissue

Ectopic salivary tissue can develop anywhere within the territory of the first and second branchial arches in the lateral neck, pharynx or middle ear. Salivary tissue is regularly found in lymph nodes within the neck and can be mistaken for metastatic disease when found in a neck dissection specimen.

Although rare, the most commonly recognised ectopic salivary tissue is the Stafne bone cyst. This presents as an asymptomatic clearly demarcated radiolucency at the angle of the mandible below the inferior dental canal. It is formed by an invagination into the bone of the lingual aspect of the mandible by an ectopic lobe of the adjacent submandibular salivary gland.

Accessory lobes

An accessory parotid lobe is the most common developmental anomaly. It occurs in as many as 20 per cent of subjects. Its position is constant arising from the horizontal component of the parotid duct as it crosses the masseter muscle. Its importance lies in the fact that any of the diseases that can affect the salivary glands may involve the accessory lobe and lead to diagnostic confusion as the possibility is not considered. This is because the symptoms and signs are not within the normal anatomical territory of the parotid.