Oropharynx Anatomy & Pathology

Question 1

Floor of mouth dermoid

MRI features?

Answer 1

• epithelial rests entrapped during
  the midline closure of the first and
  second branchial arch
• epidermoid, teratoid cyst, teratoma (all encompass dermoid)
• anterior floor of the mouth,
• sublingual, submental and
  submandibular

MRI

• cystic appearances
• no solid components
• close to midline (can be off midline)
• no enhancement
• can be low on T1

Question 2

For submucosal lesions with no obvious mucosal abnormality

What to consider?

Answer 2

Minor salivary gland tumours

Esp around palate

Question 3

Invasion of bone in oral cavity cancers

Answer 3

Beware of inflammation clouding appearances of medulla.

Use CT & MRI to assess.

Mention height of alveolar bone of mandible in cases where there is bone involvement

• Helps with pre surg planning.
• Measure vertical and horizontal

Question 4

Extension of oropharyngeal cancers

Mention invasion in each direction

Answer 4

Laterally - stylopharyngeus

Anterior - tongue

Posterior wall - pharyngeal constrictor, prevertebral fascia, retropharyngeal nodes (important area for nodal mets)

stylopharyngeus invasion

Question 5

Relevance of lesion crossing the midline?

Answer 5

Could represent spread of tumour into contralateral nodes and warrant a bilateral neck dissection.

Question 6

Post op scan interpretation

Following chemoradiotherapy

What are 3 expected patterns?

Answer 6

**Check T2 signal - should be very low, similar to muscle - this is a sign of regression. **

If T2 signal is similar to primary tumour then this can be a sign of treatment failure.

Dont rely on enhancement to make decision. PET scan can be more sensitive than MR in picking up recurrence/treatment failure nodes.

1. Vegetating tumour disappears. No residual lesions expected.
2. Deep part of tumour regresses but leaves a scar - residual low T2 signal
3. Large nodal mass regresses but leave residual low T2 lesion

Enhancement can be expected.
LN wont completely disappear but should appear low T2 following treatment - can enhance.

Question 7

For tonsillar mass - what muscle should you look for involvement?

Answer 7

1. Pharyngeal constrictor muscle
   (should be low T2 line passing posteriorly)
2. Stylopharyngeus muscle
3. Look for base of tongue involvement - for this to be involved the tonsillar lesion needs to extend inferiorly and cross the glossotonsillar sulcus.