Mucous Retention Cyst (Mucosal cyst)

These cysts are examples of retention cyst and type of extravasation cyst.

Mostly occur because of obstruction mucous secreting glands ducts. These glands cover whole of inside of mouth.

Clinical symptoms and signs. 

Slow growing swelling mostly on the inner side of lip or cheek.

Painless

Typically soft, round, pale, fluctuant and pink swelling or blue domed.

Transillumination although positive but difficult to demonstrate because the cysts are small.

Free mucous membrane over the swelling.

Differential diagnosis

Ectopic salivary gland tumours.

They are non tender and firm swellings. 

Pyogenic granuloma.

It is soft, red in colour and bleeds.

Treatment. 

Excision is the mainstay treatment and can be done under local anaesthesia. After incising mucous membrane swelling dissected all around separating it from muscles (orbicularis oris/ buccinator muscle). The mucous membrane is than closed with vicryl (absorbable sutures)