Head and Neck ImagingNasopharyngeal 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.
RH