Head and Neck Imaging

Parotid gland, pathology

Congenital anomalies
- agenesis of the parotid glands is very rare; it may be associated with other facial abnormalities.
- a cyst arising from the first branchial cleft may be located within the parotid gland: see branchial apparatus .
Inflammation
Acute inflammation is commonly caused by sialolithiasis . Mumps is the most frequent acute infection of the parotid glands. Bacterial infection may lead to intraparotid abscess formation (Fig. 1). Chronic inflammation may have an obstructive or nonobstructive aetiology. Also, see sialadenitis .
Trauma
Trauma to the parotid gland or duct may cause ductal stricture, leading to sialadenitis or formation of a sialocele . Ductal laceration may result in the development of a fistula, communicating with the skin or oral cavity.
Tumour
- The most common tumour is pleomorphic adenoma , usually appearing as a well circumscribed mass lesion in the superficial part of the parotid gland (Fig. 2). Lesions arising from the deep lobe develop primarily within the parapharyngeal space and present late with symptoms related to pharyngeal compression (see parapharyngeal space, pathology ). Also, see hemifacial spasm .
- Warthin's tumour is the second most common benign tumour of the parotid gland. Several other, but rare, benign tumours may be encountered in the parotid gland.
- The most common malignant parotid tumour is mucoepidermoid carcinoma . Other malignant parotid tumours include adenoid cystic carcinoma , acinic cell carcinoma , adenocarcinoma, head and neck and malignant pleomorphic adenoma . The parotid gland may be secondarily invaded by malignant tumours, for example arising from the external auditory canal, or by extranodal tumour spread from metastatic squamous cell carcinoma, head and neck (Fig. 3).
Intraparotid adenopathies
Within the parotid parenchyma, about 20 to 30 lymph nodes are present. These lymph nodes are the first-order drainage nodes for malignancies originating from the scalp and external ear . Squamous cell carcinoma, head and neck , and malignant melanoma are the most common malignant tumours metastasizing to the intraparotid lymph nodes (Fig. 4). Non-Hodgkin lymphoma, head and neck manifestation may also occur within these nodes. Nodal pathology with the parotid gland may also be due to reactive lymphadenopathy or a granulomatous disease, such as sarcoidosis ; also AIDS, head and neck manifestation , may cause intraparotid adenopathies.

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Fig. 01a

Axial contrast-enhanced CT images of parotid glands. Increased attenuation of left parotid gland due to sialadenitis, with intraglandular abcedation (asterisk). Note associated cellulitis of parapharyngeal space (arrowhead).
Parotid gland, pathology, Fig. 01a
Parotid gland, pathology, Fig. 02a
Parotid gland, pathology, Fig. 03a (a)
Parotid gland, pathology, Fig. 03b (b)
Parotid gland, pathology, Fig. 03c (c)
Parotid gland, pathology, Fig. 04a (a)
Parotid gland, pathology, Fig. 04b (b)