Head and Neck ImagingOropharyngeal cancer
Squamous cell carcinoma, head and neck
is the most frequent
malignant tumour of the oropharynx. There is a strong association with cigarette smoking and alcohol abuse.
Tongue base cancer tends to grow silently and deeply, and is often larger than suspected at clinical examination; it does not extend into neighbouring structures unless situated in the periphery of the tongue base. Peripheral tumours may spread to the anterior tonsillar pillar, but this is less frequently seen than spread of tonsillar cancer to the tongue base. Anterior spread into the floor of the mouth may occur (
Fig. 1). Spread to the valleculae and pyriform sinuses, and into the
pre-epiglottic space
may be seen.
Nearly all tonsillar cancers originate from the anterior tonsillar pillar. These cancers show spread anteroinferiorly to the tongue base, and superomedially spread to the soft palate, both along the palatoglossal muscle (
Fig. 2). Anterolateral spread to the
retromolar trigone
is also commonly seen. Advanced lesions may invade the
mandible
, and spread along the pharyngeal wall to the nasopharynx or through the pharyngeal wall into the
parapharyngeal space
(
Fig. 3).
Soft palate cancer may spread laterally along the tonsillar pillars.
The upper parajugular
lymph nodes are the first at risk for lymphatic spread from an oropharyngeal cancer.
Lymphadenopathy, head and neck
at other sites may be present, especially in advanced disease.
Diagnostic imaging
Imaging is performed to evaluate the
tumour extent as described above. Both
CT and
MRI are adequate
modalities;
CT has the advantage of simultaneously allowing complete evaluation of the neck
lymph nodes. In normal circumstances, the deep tissue planes at the level of the oropharynx should appear symmetrical.
Infiltration of these deep tissues is a reliable sign of
invasive disease. The apperance of superficial tissue planes is more variable, mainly because of the lymphoid tissue present in the oropharyngeal walls. Superficial tissue asymmetry, without
infiltration of the deeper tissues, can be a normal variant or caused by early cancer.
RH