Dermatologic Manifestations of Mucocele (Mucous Cyst)

Updated: Mar 27, 2019
Author: Christopher R Shea, MD; Chief Editor: William D James, MD 

Overview

Background

A mucocele (mucous cyst) is a benign, common, mucus-containing cystic lesion of the minor salivary glands in the oral cavity. The term mucocele is preferable to mucous cyst 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 mucocele are distinguished, based on the histologic features: an extravasation cyst, formed by pools of mucus surrounded by granulation tissue (mucous pseudocyst, 92%), and a retention cyst with an epithelial lining (true mucous cyst, 8%).[1]

Pathophysiology

The mechanism of mucocele formation is unclear; however, a traumatic etiology rather than an obstructive phenomenon is considered more likely. Chaudhry et al showed that the escape of mucus into the surrounding tissue after severing the excretory salivary ducts led to mucocele formation.[2] The frequent location of the mucocele on 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 mucocele, Chaudhry et al demonstrated that ligation and cutting of the salivary glands' ducts in rodents did not result in mucocele formation.[2] Lymphatic vessels may also contribute to the early stages of mucocele development. Specifically, the growing mucocele may induce a pressure gradient that causes lymphatics to swell with interstitial fluid, eventually rupturing and delivering this fluid back to the mucocele.[3]

In a study of 138 pediatric cases, Martins-Filho et al concluded that trauma is the main etiologic factor involved in the development of mucoceles in children. The mucus extravasation phenomenon is the most common histologic type in this age group. Although rare, the retention type seems to be more common in lesions on the floor of the mouth.[4]

After reviewing 1824 adults, Chi et al confirmed previous findings concerning the clinicopathologic features of oral mucoceles. Although special variants occur only infrequently, they need to be identified to avoid misdiagnosis.[5]

Etiology

A traumatic etiology is favored for mucoceles. Animal models and the location of these lesions in areas of high traumatic exposure support this theory.[6, 7, 8, 9]

Epidemiology

Frequency

The prevalence of oral mucocele is 2.5 lesions per 1000 population.[10]

Race

Mucoceles are most frequent in whites.

Sex

The incidence of mucocele is about equal in males and females.[11]

Age

Although patients of all ages can be affected, more than half of mucocele cases occur in those younger than 30 years. In a large oral pathology series in children and adolescents, mucocele was the most common entity diagnosed (33% of cases), and the lip mucosa was the site most often involved (48%).[12] However, mucocele is uncommon in neonates and infants.[13] Very rarely, congenital onset has been reported.[14]

Mucous retention cysts are more frequent in older persons; conversely, the majority of mucoceles in younger patients represent the extravasation type.[15]

Mucoceles of the glands of Blandin-Nuhn (present on the ventral surface of the tongue) appear to be more prominent in young patients.[15]

Prognosis

Mucocele, a benign condition, is self-limited in most cases. Patients with mucoceles have an excellent prognosis; however, recurrence is common unless the associated salivary gland is resected.

 

Presentation

History

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

People with superficial mucoceles (mucous cysts) may report single or multiple blisters that often spontaneously burst, leaving shallow ulcers. These lesions completely heal within a few days. Sometimes, lesions recur in the same site.

The classic presentation of mucoceles is as a shiny, dome-shaped papule that waxes and wanes over several months.

A mucocele 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.

The appearance of superficial mucoceles as a consequence of chronic graft versus host disease has been reported in patients receiving allogeneic bone marrow transplants. They typically are asymptomatic and therefore may not be identified.[16]

Physical Examination

The clinical presentation of mucoceles depends on the depth of the lesion.

Superficial mucocele

The mucus accumulates immediately below the mucosa, resulting in small translucent vesicles (0.1-0.4 cm in diameter) on the soft palate, retromolar region, and buccal mucosa.

In time, these vesicles may burst spontaneously or by trauma, leaving shallow ulcers or erosions.

Classic mucocele

This form presents as a collection of mucus in the upper submucosa producing a well-defined, mobile, painless, dome-shaped swelling. These lesions often exhibit a smooth, blue surface. The size varies from a few millimeters to several centimeters in diameter; 75% of the lesions are less than 1 cm in diameter.

Eventually, the surface turns irregular and whitish due to multiple cycles of rupture and healing caused by trauma or puncture.

The most frequent locations are the lower lip, floor of the mouth, cheek, palate, retromolar fossa, and dorsum of the tongue; the upper lip is usually spared.

Larger lesions most often affect the floor of the mouth; these are called ranulas because of the similarity to the throat pouch of frogs. A ranula can extend beyond the oral cavity, even to the upper mediastinum or skull base.

When the mucus accumulates in the deep soft tissues, the presentation is as an enlarging, painless mass assuming the pink coloration of the mucosa.

 

DDx

Differential Diagnoses

 

Workup

Imaging Studies

Consider the additional studies described below to evaluate the anatomical extension of a deep mucocele (mucous cyst).

Plain radiographs show nonspecific soft-tissue density.

Ultrasonograms show a rounded or lobulated, hypoechoic mass with well-defined borders.

CT scans frequently demonstrate a circumscribed, water-density mass.

MRI shows a homogeneous, low-intensity lesion on T1-weighted images. T2-weighted images reveal an increased signal and sharp borders.

Other Tests

Fine-needle aspiration is commonly used in the evaluation of deep lesions. The aspirate smears usually show sparsely cellular mucoid material with a few histiocytes and inflammatory cells.

Histologic Findings

The specimens show collections of eosinophilic mucus admixed with some inflammatory cells in the upper portion or deep submucosa (see the image below). The mucus is periodic acid-Schiff (PAS) positive, diastase resistant, positive for colloidal iron and Alcian blue (pH 2.5), and hyaluronidase resistant. These properties of staining indicate a nonsulfated acid mucopolysaccharide, such as sialomucin.[17] The mucus has an epithelial rather than a fibroblastic origin.

The submucosa shows a mucus-filled, cystlike cavit The submucosa shows a mucus-filled, cystlike cavity below the squamous mucosa. Minor salivary gland lobules are present in the submucosa.

Granulation tissue with an acute inflammatory infiltrate mainly forms the wall of the cystlike cavity (see the image below).[17] In time, the wall surrounding the cavity contains a variable number of fibrocytes and chronic inflammatory cells. An epithelial lining, most likely derived from the minor salivary ducts, is rarely identified in these biopsy specimens. The associated salivary gland is usually seen deeper in the connective tissue. This lesion may have lymphocytic infiltrates, ductal distention, degeneration of acini, and variable fibrosis.

The wall of the lesion is usually formed by connec The wall of the lesion is usually formed by connective tissue, inflammatory cells, foamy macrophages (lower left corner), and salivary gland acini (upper right corner).

Early in mucocele development, dilated lymphatics may be present at the periphery of the area where mucus is retained.[3]

Secondary changes (eg, parakeratosis, acanthosis, atrophy) may occur in the epidermis or squamous mucosa. Clear-cell change with signet-ring cell formation has been reported.[18] Transmucosal elimination of mucus has been reported. The superficial mucocele is a subepithelial blister. The roof of the lesion is formed by attenuated mucosa, while the floor consists of corium with sparse inflammatory infiltrates.

Some lesions appear to be intraepithelial blisters due to the regeneration of epithelium across the denuded base. The content of the lesion consists of variable amounts of eosinophilic mucus admixed with polymorphonuclear cells. Salivary gland ducts may open into the floor of the blister, and salivary gland lobules may be identified in deeper tissues.

Rare histologic variants of oral mucocele include those with features of myxoglobulosis (globular structures with intraluminal eosinophilic, lamellar, amorphous, or fibrillary material), papillary synovial metaplasia–like change, superficial mucocele presenting as a mucus-containing subepithelial blister, and a form exhibiting extensive clear cytoplasm and signet-ring alterations.[19]

 

Treatment

Medical Care

Patients with asymptomatic, superficial mucoceles (mucous cysts) may require reassurance only. Partial or total electrodesiccation and intralesional injections of triamcinolone acetonide have been reported as treatments for mucoceles. Topical clobetasol propionate 0.05% has been reported as an effective intervention for multiple, recurrent mucoceles.[20]

Intralesional sclerotherapy using polidocanol or sodium tetradecyl sulfate has also been used successfully.[21, 22] Intralesional injection of absolute ethanol has also been reported as an alternative therapy for mucocele of the glands of Blandin-Nuhn.[23]

Surgical Care

For definitive management, if indicated, the minor salivary gland may be excised, just as in cases with persistent irritation.

The treatment of choice for a deep mucocele and the classic form is surgical excision, which should include the immediate adjacent glandular tissue. In one study, the risk of recurrence following surgical resection in children varied significantly by location and age, with a 50% recurrence rate in cases located on the ventral mucosa of tongue, compared with 8.8% recurrence in lesions of the labial/buccal mucosa. Recurrence was much more common in the patients younger than 30 years than in older patients.[24]

Cryosurgery with liquid nitrogen spray or cryoprobe is an alternative therapeutic modality.[25, 26] After day 4 to week 1, a necrotic surface is observed in the treated area. The latter separates from the surrounding mucosa in 1-2 weeks, exposing a new epithelialized surface. The advantages of the procedure include a simple application, minor discomfort during the procedure, and a low incidence of complications (eg, secondary infection, hemorrhage); however, recurrence is possible.

Another therapeutic strategy is argon laser treatment, typically administrated at a constant pulse duration of 0.3 seconds, using a laser beam diameter of 1.5-2 mm and a power setting of 2-3 W. Lesions presenting as firm nodules are treated with a continuous exposure and a power setting of 2.5-3.5 W. The necrotic area posttreatment is well defined by day 8-12, with complete wound healing in approximately 2 weeks. The only reported complications are swelling and mild discomfort for up to 10 days.[27] The advantages of argon laser over cryosurgery consist of less discomfort in the postoperative period, less edema and irritation, and a reduced healing time. A disadvantage of this therapeutic alternative is the requirement of specialized equipment.

The use of carbon dioxide laser appears to be a superior treatment modality for mucocele, with minimal recurrence.[28] It has the advantages of allowing precise surgical technique, lack of bleeding for a clear operative field, minimal wound contraction and scarring, and a short operative time.[29, 30, 31] As such, it has been proposed to be particularly useful in the treatment of those who are intolerant of long procedures, including children. A disadvantage is the requirement of expensive, specialized equipment, and necessary protection for both the patient and physician performing the laser vaporization.[30]

Erbium laser treatment has also been described in a pediatric patient, with excellent results.[32]

Diode laser vaporization (940 nm in contact mode) was used successfully in one reported patient with an extravasation-type mucocele of the lower lip.[33]

Microwave ablation has been used with good results in a small number of patients.[34]

Consultations

Possible consultations may include the following:

  • Dermatologist

  • Dermatologic surgeon

  • Oral medicine specialist

  • Oral surgeon

Complications

Secondary infection and local bleeding are rare complications. Traumatic neuroma may occur as a sequela following laser or cryosurgery.[35]

 

Medication

Medication Summary

Local injection of corticosteroids has been used for treating mucoceles (mucous cysts), and some authors consider it a first-line therapy[36] ; however, a high frequency of recurrence has been reported with this treatment.

Corticosteroids

Class Summary

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. They modify the body's immune response to diverse stimuli.

Triamcinolone (Aristocort)

Triamcinolone is used for inflammatory dermatoses responsive to steroids. It decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing capillary permeability. Intramuscular injection may be used for widespread skin disorders, or intralesional injections may be used for localized skin disorders.