The ranula is a mucous retention cyst secondary to obstruction of a minor
salivary gland or the sublingual gland. They represent a unilocular cyst
in the sublingual space. One often sees the tail. They are considered simple
if they are confined to the sublingual space. If the capsule breaks and
there is extension from the sublingual space into the adjacent submandibular
or parapharyngeal space, they are considered a diving or plunging ranula.