Ranulas are mucous extravasation cysts typically presenting in young adults, arising from the sublingual gland, characterised by the presence of clear, thick, mucoid fluid and typically appearing as a well-defined cystic lesion in the sublingual space on imaging.
Description
A ranula is a type of mucocele that is found on the floor of the mouth. Ranulas present as a swelling of connective tissue consisting of collected mucin from a ruptured salivary gland duct, which is usually caused by local trauma. If small and asymptomatic, ranulas may not require any treatment, however larger lesions can cause discomfort, functional disturbance, or cosmetic concerns.
Pathogenesis
Ranulas occur as a result of rupture of the ductal system of the sublingual gland, often due to trauma, resulting in an extravasation of mucin into the surrounding tissues. This pooling of mucin incites a granulomatous inflammatory reaction and the formation of a pseudocyst. Unlike a true cyst, a pseudocyst lacks an epithelial lining.
Subtypes
Ranulas can be categorised into two types:
- Simple ranula: Located in the floor of the mouth.
- Plunging or cervical ranula: A ranula that extends through the mylohyoid muscle into the neck.
Epidemiology, Risk Factors & Associations
- More common in young adults (second and third decades of life).
- No significant gender bias.
Clinical Features
- Painless, fluctuant swelling in the floor of the mouth, often unilateral.
- May cause difficulty with speaking, eating or swallowing if large.
- Bluish hue if close to the surface of the mucosa.
Complications
- Enlargement causing functional disturbance or cosmetic concern.
- Recurrence after treatment.
Pathological Features
Histopathology
- Macroscopic: Fluctuant, translucent-blue cystic lesion.
- Microscopic: Granulation tissue surrounding pools of extravasated mucin.
Radiological Features
General Features
- Well-defined cystic lesion in the sublingual space, extending into the submandibular space in the case of a plunging ranula.
CT
- Non-contrast: Well-defined water attenuation cystic lesion.
MRI
- T1: Hypointense.
- T2: Hyperintense.
- T1 Gad+: No internal enhancement.
US
- B-mode: Anechoic or hypoechoic well-defined lesion.
Diagnosis
The diagnosis is usually clinical, based on the typical location and appearance of the lesion. Imaging is performed to determine the extent of the lesion. Biopsy or aspiration is typically not performed due to the risk of spillage of mucin leading to recurrence or infection.
Differential Diagnosis
- Dermoid cyst: Often has an echogenic centre on ultrasound due to keratinous debris.
- Abscess: Associated with signs of infection. Typically presents with rapid onset.
Prognosis
Prognosis is excellent, but recurrence after treatment is a common problem, particularly for plunging ranulas.
Management
Conservative management may be considered for small, asymptomatic lesions. Surgical options for larger lesions include marsupialisation, excision of the lesion, or removal of the associated sublingual gland. The choice of treatment depends on factors such as the size and location of the ranula and the patient’s general health.