Ranulas

The word ranula is derived from the Latin rana for frog, referring to the blue translucent swelling in the floor of the mouth that reminded people of the underbelly of a frog.

Ranulas are rare cystic lesions of the salivary gland and usually occur in the teens and twenties. They are benign and result from obstruction of sublingual or minor salivary glands. When confined to the the sublingual space, they are called simple ranulas. When they extend from the sublingual space to involve the submandibular or parapharyngeal spaces, they are designanted plunging or diving ranulas. Plunging ranulas typically extend posteriorly beyond the free edge of the mylohyoid muscle.

Differential considerations include:

• Submandibular or sublingual space epidermoid: Unilateral. Thin, nonenhancing wall. Sublingual space epidermoid may look identical to a simple ranila.
• Second branchial cleft cyst: Unilocular cyst in the posterior aspect of the submandibular space. Does not have extension into the sublingual space.
• Lymphangioma of the oral cavity: Lobulated, multilocular cystic mass that doesn't generally involve the sublingual space.
• Infected submandibular lymph node: Look for other similar lymph nodes
• Abscess: Look for other signs of infection.
• Mucocele: Submandibular gland retention cyst that doesn't involve the sublingual space.

References

Coit WE, Harnsberger HR, Osborn AG, Smoker WR, Stevens MH, Lufkin RB. Ranulas and their mimics: CT evaluation. Radiology. 1987 Apr;163(1):211-6.