Ranula

Simple ranula: post-inflammatory retention cyst, epithelial lining, located above the mylohyoid muscle
Diving ranula: extravasation pseudocyst, occurs when a large ranula ruptures into the submandibular space, no epithelial lining
Also known as a sublingual gland mucocele, mucous retention cyst
Trauma or inflammation of the sublingual salivary gland resulting in obstuction and saliva collection
Simple ranulas are well-defined and thin walled (ovoid)
Diving ranulas show a sublingual space collapsed "tail" and submandibular extension (comet-shaped)
Simple ranulas are typically <3 cm; diving ranulas are often <6 cm but can be massive
On CT: low-density, unilocular lesion, subtle ring enhancement, florid enhancement if infected
On MR: low signal on T1; very high signal on T2; T1 post-contrast shows wall enhancement and high signal if infection present
Median presentation age is 30, more common in Pacific islanders