eRadiograph Volume 7: Imaging of Oral Cavity | Page 20

mass. However, these may remain clinically silent appearance of a neck mass. These
tend to be aggressive tumors with 20% survival rate.
The contents of the oropharynx are mucosa, lingual/palatine tonsils, minor salivary
glands, constrictor muscles and fascia.
The outer boundary of the oropharynx is the middle layer of deep cervical fascia
(Buccopharyngeal fascia). Inside this fascia lies the superior and middle constrictor
muscles. The pharyngobasilar fascia lies inside buccopharyngeal fascia, attaching the
superior constrictor to the base of the skull. Neoplastic disease can spread along the
superior constrictor muscle, pharyngobasillar fascia to the base of skull.
The superior constrictor muscle is connected to the buccinators muscle via the
ptyergomandibular raphe, which runs from the posterior mylohyoid line to the medial
pteryrgoid plate. This is a potential route of spread from the oropharynx to the oral
cavity/buccal space, as well as the oropharynx and the central skull base, OP and
pterygoid muscles in masticator space.

Oropharyngeal carcinomas tend to be infiltrative, growing along muscle planes, thus
making accurate assessment of size is difficult. Base of tongue lesions may be difficult
to discern from musculature due to the paucity of fat. Invasion of prevertebral muscles
from posterior pharyngeal wall may be difficult. Loss of normal fat signal in
retropharyngeal space is usually a useful sign, similarly preservation of fat indicates no
invasion. Adjacent muscle enhancement can be a useful sign though, may occur in
inflammation also. Tumour encasing the carotid artery by 270 degrees is quite specific
for invasion.
Staging
It is very important to appropriately stage cancer. The stage predicts survival rate,
guides management. TNM classification is the main stay of staging.
The T portion of TNM staging defines size of malignancy by size or contiguous
extension.

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Imaging of Oral Cavity

Squamous cell carcinomas account for apporoximatelly 15% of all neoplasms arising
in the oropharynx. The incidence of oropharyngeal carcinoma is increasing due to HPV
infection – HPV is sexually transmitted. HPV virus infects the transitional epithelium in
the upper aerodigestive tract and anogenital regions. Individuals with HPV oral
infection are at a 15 fold higher risk of oropharyngeal cancer and a 50 fold higher risk
for HPV positive. Head neck squamous cell cancer, HPV positive cancers however, have
significantly better outcomes than HPV negative patients.