eRadiograph Volume 7: Imaging of Oral Cavity | Page 321

gland acts as differentiator between masses arising on the submandibular gland and
growing exophytically versus extrinsic masses. If the mass is external to the anterior
facial vein it is an extrinsic mass lesion.
Pathology
Ranula
These represent mucous retention cysts or mucocele arising from a sublingual or minor
salivary gland, usually secondary to trauma or inflammation. These appear as thin
walled homogenous fluid intensity lesions in the sublingual space. There may be
septations or non enhancement as a result of previous or ongoing inflammation. A
ranula may rupture and extend posteriorly from the sublingual space into the
submandibular space behind the mylohyoid. This is known as a diving or plunging
ranula. Occasionally a ruptured ranula may extend through a defect in the mylohyoid
into the anterior submandibular space. These ruptured ranulas are akin to pancreatic
pseudocysts as they do not have a wall, and similar to pancreatic pseudocysts
containing proteolytic enzymes allowing the lesion to infiltrate, digest adjacent tissues.

On imaging thyroglossal cysts appear as homogenous fluid density lesions with a thin
wall. On CT they are hypodense, On MRI they are hypointense on T1,
hyperintense on T2. Occasionally with highly protenecous fluid contents they
may be hyperintense on T1. There is usually no enhancement of the wall of the
thyroglossal cyst. Occas