Mucocoele

• A mucococele (also mucocele) is the accumulation of mucus in either the connective tissue of within a salivary duct
• The term encompasses both mucus extravasation phenomenon and mucous retention cyst

Epidemiology

• No gender predilection
• Average age onset is 25 years

Clinical Features

Mucocoele lower lip

• Usually presents as recurrent swelling with intermittent mucous discharge (patients commonly report "drainage and re-filling")
• Commonly there is a history of trauma to the site but this is not always the case
• May develop at any site, but common locations are:
  • Lower labial mucosa (81.9%)
  • Floor of mouth (5.8%) ← known as a ranula
  • Ventral tongue (5.0%)
  • Buccal mucosa (4.8%)
• Rare in upper lip
• Clinically appears translucent or bluish in colour (∵ of mucous contents)
  • Transillumination is present if the lesion is large enough
• Palpation is usually soft and can feel fluctuant

Differential Diagnosis

• Be suspicious of an alternative diagnosis at less common sites (e.g. in upper lip, tumours of minor salivary glands are more common)

Aetiology and Pathogenesis

Formation of mucocoeles

• Not true cysts because there is no epithelial lining (technically, they are polyps)
• Mucous extravasation phenomenon
  • Extravasation mucoceles are caused by a leaking of fluid from surrounding tissue ducts or acini
  • Usually secondary to trauma causing a rupture of the ducts
• Mucus retention cyst
  • Retention mucoceles are formed by dilation of the duct secondary to its obstruction (sialolith or dense mucosa)

Investigations

• Diagnosis is made on histology and clinical examination

Histology

Histopathologic image of extravasation type mucocele of the lower lip. H & E stain.

• Mucin surrounded by granulation tissue
• As inflammation is usually also present neutrophils and foamy histiocytes are also identified

Management

• Surgical excision of the cyst and associated minor salivary gland (usually under local anaesthetic)
  • Key to avoiding recurrence is to eliminate the adjacent surrounding glandular acini and removing the lesion down to the muscle layer
• Aspiration does not lead to a lasting benefit as the salivary glands quickly refill the mucocoele
• Some reports of using cryotherapy and laser therapy

Prognosis and Complications

• Lesions can recur (different rates reported by ~3%)

Follow-up

• No routine follow-up needed
• Usually suitable for results to be presented to patient using remote consultation (telephone or results in post)