Head and Neck Imaging

Adenoid cystic carcinoma

malignant epithelial tumour which develops in the major and minor salivary glands. The name is misleading as cystic structures are unusual in this tumour; cystic tumour areas are more typically seen in mucoepidermoid carcinoma or Warthins tumour. It is sometimes also called cylindroma, an old name which is better abandoned as it includes several nonrelated types of neoplasms.

Adenoid cystic carcinoma is fairly uncommon in the parotid gland (2- 5% of all tumours in this gland), but it is the more common in the lesser major salivary glands (submandibular gland and sublingual gland) and the minor salivary glands (25 - 35% of minor salivary gland tumours are adenoid cystic carcinomas). This tumour is mainly seen in the mid-forties; presenting symptoms are a mass lesion, sometimes a dull pain and/or paralysis of a cranial nerve (see facial nerve palsy) when arising from the parotid gland) related to the marked tendency of this tumour to invade nerves. Invasion of nerves is an almost invariably microscopic finding, and definitely more often seen with this neoplasm than with any other head and neck cancer. Skip lesions within nerves occur; negative surgical margins therefore have little significance.

The treatment of choice is wide surgical resection; a better local tumour control rate can be obtained with postoperative radiation treatment. The long-term outcome for patients with this tumour is bad (about 75% survival rate at 5 years, but only about 15% at 20 years). The relatively high recurrence rate may be due to uncomplete primary surgical treatment, related to unrecognized perineural tumour extension. Distant metastatic deposits occur late in the disease, often in the lungs; tumour progression is slow and patients may live a long time with metastatic disease.

The radiographic characteristics of adenoid cystic carcinoma are nonspecific. As they grow submucosally, they are often locally more extensive than clinically suspected (Fig.1). Given the strong predilection for perineural tumour spread head and neck, MRI is the method of choice for visualization of tumour extent (Fig.2). Also, see sublingual space (VI:2), Fig. 1.

 

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Fig.1

Patient presenting with hoarseness; endoscopically, a submucosal mass lesion is suspected. The axial T2-weighted MR image (a) shows a hyperintense mass lesion (arrows) in the subglottis and distal hypopharynx. On the sagittal gadolinium-enhanced T1-weighted image (b), the mass is seen to infiltrate the larynx (upper arrowhead), proximal trachea (lower arrowhead), distal hypopharynx (upper arrow) and proximal oesophagus (lower arrow).
Adenoid cystic carcinoma, Fig.1 (a)
Adenoid cystic carcinoma, Fig.1 (b)
Adenoid cystic carcinoma, Fig.2 (a)
Adenoid cystic carcinoma, Fig.2 (b)
Adenoid cystic carcinoma, Fig.2 (c)