Mucous Cyst

Introduction

Background

A mucous cyst (MC) is a benign, common, mucus-containing cystic lesion of the minor salivary glands in the oral cavity. Some authors prefer the term mucocele since most of these lesions are not true cysts in the absence of an epithelial lining. The lesions can be located directly under the mucosa (superficial mucocele), in the upper submucosa (classic mucocele), or in the lower corium (deep mucocele). Two types of MCs occur based on the histologic features of the cyst wall: a mucous extravasation cyst formed by mucous pools surrounded by granulation tissue (92%) and a mucous retention cyst with an epithelial lining (8%).

Pathophysiology

The mechanism of formation of the MC is not totally clear; however, a traumatic etiology rather than an obstructive phenomenon is favored. Chaudhry et al showed that the escape of mucus into the surrounding tissue after severing the excretory salivary ducts led to the formation of the MC. The frequent location of the MC in the lateral aspect of the lower lip also supports the role of trauma as an etiologic factor. Although obstruction may play a role in the etiology of the MC, Chaudhry et al demonstrated that the ligation and cutting of the salivary glands' ducts in mice and rats did not create the MC.

Frequency

United States

The prevalence of an oral MC is 2.5 lesions per 1000 population.

Mortality/Morbidity

This benign condition is self-limited in most cases.

Race

A MC is most frequent in whites.

Sex

The sexual incidence is about equal.

Age

Although patients of all ages can be affected, more than one half of MC cases occur in those younger than 30 years. Mucous retention cysts are more frequent in older persons than in younger persons.

Clinical

History

The clinical presentation varies by the type and the location of the lesion.

• People with superficial MCs may complain of single or multiple blisters that often spontaneously burst, leaving shallow ulcers.
  • These lesions completely heal in a period of a few days.
  • Sometimes, lesions recur in the same site.
• The classic MC presents as a shiny, dome-shaped papule that waxes and wanes over several months.
• An MC located in the deep soft tissue has a slow growth phase, resulting in a firm, deep mass.
• Rare cases have been described in the neck arising from ectopic salivary glands; these lesions are associated with cheilitis glandularis apostematosa.

Physical

The clinical presentation depends on the depth of the lesion.

• Superficial MC
  • The mucus accumulates immediately below the mucosa, resulting in small translucent vesicles (0.1-0.4 cm in diameter) in the soft palate, the retromolar region, and the buccal mucosa.
  • In time, these blisters burst spontaneously or by trauma, leaving shallow ulcers or erosions.
• Classic MC
  • This form presents as a collection of mucous material in the upper submucosa producing a well-defined, mobile, and painless dome-shaped swelling.
  • These lesions often exhibit a smooth, blue surface.
  • The size varies from a few millimeters to several centimeters in diameter, but 75% of the lesions are smaller than 1 cm in diameter.
  • Eventually, the surface of the lesion turns irregular and whitish due to multiple cycles of rupture and healing caused by trauma or puncture.
  • The most frequent locations are in the lower lip, the floor of the mouth, the cheek, the palate, the retromolar fossa, and the dorsal surface of the tongue; however, these lesions spare the upper lip.
  • Most of the larger lesions commonly affect the floor of the mouth; these are called ranula because of the similarity to the throat pouch of frogs. This collection of mucus can extend beyond the oral cavity and as far as the upper mediastinum or skull base.
  • When the mucus accumulates in the deep soft tissues, the presentation is of an enlarging, painless mass assuming the pink coloration of the mucosa.

Causes

A traumatic etiology is favored. Animal models and the location of these lesions in areas of high traumatic exposure support this theory.