Mucocele

A mucocele is a benign, mucus filled lesion of the oral mucosa caused by damage or obstruction of a minor salivary gland duct, resulting in mucus extravasation into the connective tissue (extravasation mucocele, about 75 percent, with no epithelial lining) or retention in a dilated duct (retention mucocele, with epithelial lining). It is the commonest minor salivary gland lesion, with an incidence of about 2.5 per 1000 people, and is common in children and young adults.

The lower lip is involved in about 70 to 80 percent, followed by the ventral tongue (glands of Blandin-Nuhn), buccal mucosa, floor of mouth and palate; upper lip lesions are rare and may suggest a tumour. The most frequent cause is trauma, such as lip biting, lip sucking, and accidental injury. Ranula is a mucocele of the sublingual gland in the floor of the mouth; plunging ranula extends through the mylohyoid into the neck. Superficial mucoceles heal spontaneously within weeks in some patients, whereas deep lesions persist or recur.

• Painless, dome shaped, translucent bluish or normal coloured swelling of 2 mm to 2 cm, soft and fluctuant, on the lower lip, ventral tongue or buccal mucosa.
• Rapid appearance, rupture with release of clear sticky fluid, and recurrence; may fluctuate in size with eating.
• Superficial mucocele: thin walled, blue, vesicle like in the soft palate or retromolar area.
• Ranula: unilateral blue swelling in the floor of the mouth, which may reach 5 cm and displace the tongue; plunging ranula presents as a soft, painless neck swelling.
• Red flags: firm, non-fluctuant, persistent lesion on the upper lip or palate (neoplasm), ulceration, rapid growth, lymphadenopathy, or airway or swallowing compromise (large ranula).

• Clinical diagnosis from the typical location, history of trauma, and fluctuant bluish swelling.
• Transillumination and aspiration of mucus (clear, viscous) when needed; diagnostic aspiration only for ranula.
• Ultrasound for neck extension (plunging ranula) and to distinguish from lymphatic malformations; MRI or CT for deep extension, with cystic mass in the sublingual space and a "tail sign" for plunging ranula.
• Histology after excision: extravasated mucin pool surrounded by granulation tissue and foamy histiocytes; sectioning of adjacent minor salivary glands.
• Exclude lymphangioma, haemangioma, venous lake, dermoid cyst, mucoepidermoid carcinoma, pleomorphic adenoma, lipoma, and salivary duct calculus.

• Observation: small superficial lesions of under 1 cm often resolve spontaneously within 4 to 6 weeks; avoid habitual biting and do not puncture.
• Surgical excision under local anaesthesia (lidocaine 2 percent with adrenaline 1:80 000, 1 to 2 mL) is the standard: elliptical incision around the lesion, careful blunt dissection to avoid rupture, removal of the feeding minor salivary glands, and suturing with 4-0 absorbable sutures; recurrence is about 5 to 15 percent and is higher if the adjacent glands are left behind.
• Alternatives: carbon dioxide laser vaporisation or excision, cryotherapy (liquid nitrogen, 2 freeze thaw cycles of 20 seconds), micro marsupialisation (suture passed through the lesion to maintain a drainage tract for 7 to 14 days), and intralesional corticosteroid injection (triamcinolone acetonide 10 mg/mL, 0.1 to 0.3 mL, repeated at 2 to 4 weeks) for small lesions.
• Ranula: excision of the ranula with the involved sublingual gland (definitive, recurrence 1 to 2 percent), or marsupialisation alone (recurrence 60 to 90 percent); plunging ranula is treated by sublingual gland excision through the intraoral route.
• Sclerotherapy: OK-432 (picibanil) 0.1 mg injected into ranula in 1 to 3 sessions where available.
• Postoperative care: chlorhexidine 0.12 percent mouthwash 10 mL twice daily for 7 days, soft diet, and analgesia with paracetamol 1 g every 6 hours (children 15 mg/kg every 6 hours).
• Follow up: at 1 and 4 weeks; histology review.
• Counselling: stop lip biting, and recurrence may follow if the habit persists; return for rapid regrowth.