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