Head and Neck Imaging

Nasopharyngeal cancer

Overall, malignant nasopharyngeal tumours are uncommon, but a much higher incidence of nasopharyngeal cancer is seen along the south-east coast of China, including Hong Kong and Macao. An association with the Epstein-Barr virus is observed, but other risk factors have also been reported. The age distribution is much younger than for other head and neck cancers.
Nasopharyngeal carcinoma has a lymphoid stroma, and is also known as undifferentiated carcinoma of nasopharyngeal type or lymphoepithelioma .
Clinical picture
The most common presenting symptom is a neck mass (caused by neck adenopathies). Nasal obstruction is also common; epistaxis may be present. Hearing loss secondary to dysfunction of the eustachian tube may also be the first symptom; unilateral serous otitis media in an adult patient should always raise the possibility of a nasopharyngeal tumour. With disease progression, other symptoms may arise, such as those caused by skull base invasion (dysfunction of cranial nerves) or by orbital invasion.
Diagnostic imaging
Imaging is required for both staging and treatment planning. MRI is the preferred imaging modality, but complementary CT may be needed for evaluation of early bone invasion.
Many of these tumours arise in Rosenmuller's fossa . Lateral spread through an anatomical opening in the pharyngobasilar fascia , provides access to the parapharyngeal space and is commonly seen (Fig. 1); from here, the mass may spread to the skull base or progress towards the masticator space . Direct superior extension in or through the skull base is seen in about one quarter of patients; this commonly occurs at the level of the foramen lacerum and/or petroclinoid fissure (Fig. 2); if the lesion spreads to the masticator space, superior extension along the mandibular nerve (through the foramen ovale) is commonly observed (Fig. 3). Inferior extension along the pharyngeal walls, and anterior spread to the nasal cavity are also common. Nearly all patients have lymphatic spread at presentation; the retropharyngeal lymph nodes are nearly always the first involved (see retropharyngeal space, pathology ).
Treatment
Nasopharyngeal carcinoma is treated by radiotherapy. The control rates are higher for lymphoepithelioma than for squamous cell carcinoma, head and neck at other head and neck sites.

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Fig. 02a

Gadolinium-enhanced T1-weighted spin-echo images through the nasopharynx. A. Axial image showing a large soft tissue mass, centered on the right fossa of Rosenmuller (normal left fossa of Rosenmuller, arrow). The lesion extends in the right parapharyngeal space, displacing the tensor veli palatini muscle (arrowheads). B. Coronal image showing spread through the skull base, at the level of the foramen lacerum, into the cavernous sinus (arrow); the cavernous portion of the internal carotid artery is displaced by the tumor mass. Tumor spread is seen through the lateral wall of the right sphenoid sinus, also containing inflammatory material.
Nasopharyngeal cancer, Fig. 01a
Nasopharyngeal cancer, Fig. 02a (a)
Nasopharyngeal cancer, Fig. 02b (b)
Nasopharyngeal cancer, Fig. 03a (a)
Nasopharyngeal cancer, Fig. 03b (b)