An Atlas of Lumps and Bumps: Part 13

AUTHORS:
Alexander K. C. Leung, MD^1,2—Series Editor • Benjamin Barankin, MD³ • Joseph M. Lam, MD⁴ • Kin Fon Leong, MD⁵

AFFILIATIONS:
¹Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada
²Alberta Children’s Hospital, Calgary, Alberta, Canada
³Toronto Dermatology Centre, Toronto, Ontario, Canada
⁴Department of Pediatrics and Department of Dermatology and Skin Sciences, University of British Columbia, Vancouver, British Columbia, Canada
⁵Pediatric Institute, Kuala Lumpur General Hospital, Kuala Lumpur, Malaysia

CITATION:
Leung AKC, Barankin B, Lam JM, Leong KF. An atlas of lumps and bumps, part 13. Consultant. 2022;62(2):e33-e35. doi:10.25270/con.2022.01.00005

DISCLOSURES:
Dr Leung is the series editor. He was not involved with the handling of this paper, which was sent out for independent external peer review.

CORRESPONDENCE:
Alexander K. C. Leung, MD, #200, 233 16th Ave NW, Calgary, AB T2M 0H5, Canada (aleung@ucalgary.ca)

EDITOR’S NOTE:
This article is part of a series describing and differentiating dermatologic lumps and bumps. To access previously published articles in the series, visit https://www.consultant360.com/resource-center/atlas-lumps-and-bumps.

Ranula

A ranula is a large mucus-containing, cyst-like mass caused by extravasation and accumulation of mucus from a major salivary gland (most commonly the sublingual salivary gland) into the surrounding tissue in the floor of the mouth.^1-4 The condition can be congenital or iatrogenic.^2,5 Congenital ranulas may result from an imperforate salivary duct or ostial adhesion.⁴ Iatrogenic ranulas may result from trauma to or obstruction of an excretory duct of a major salivary gland.^2,6 Because ranulas are lined with granulation tissue instead of epithelium, they are considered a type of pseudocyst.^1,4

The prevalence rate of ranulas is 2 cases per 10,000 persons.^3,5,6 Individuals in their second and third decades of life are more commonly affected.^2,4,7 The sex ratio is approximately equal.^2,6 There is no racial predilection.⁶

Typically, a simple (or intraoral) ranula presents as a slow-growing, thin-walled, translucent to bluish, fluctuant, painless, round or oval swelling in the floor of the mouth that resembles the belly of a frog (Figures 1 and 2).^3,5,6 In fact, the term “ranula” is derived from the Latin word “rana,” meaning belly of the frog.⁴ Large lesions might lead to speech impairment, difficulty with mastication, dysphagia, and rarely, airway blockage and obstructive sleep apnea.^2,3

A plunging (or cervical) ranula occurs when a portion of the sublingual gland herniates through a dehiscence in the mylohyoid muscle with its extravasated mucin into the submandibular and submental space.^1,7,8 Typically, a plunging ranula presents as an asymptomatic, fluctuant to soft cervical mass without swelling of the floor of the mouth. The swelling is usually unilateral but may cross the midline.⁶ A mixed ranula, on the other hand, presents with both intraoral and cervical swelling.¹

Mucocele

Mucoceles are the most common mucus cyst occurring in the oral cavity.^9,10 The incidence in the general population is estimated to be 0.2.%.⁶ A mucocele is caused by a traumatic severed or blocked duct of a minor salivary gland.^6,11,12 A traumatic severed duct of a minor salivary gland is most often caused by lip biting during chewing, habitual lip biting, or accidental injury to the lip.^6,9,13 This leads to extravasation and accumulation of mucin in submucous tissue, referred to as an extravasation mucocele.¹⁰ The extravasated mucin is surrounded by condensed connective tissue with a variable amount of inflammation.^10,14 No epithelial lining is present.¹⁵ The lower lip is the most frequent site of the extravasation cyst because it is the area most often susceptible to trauma.^13,16 A retention mucocele, on the other hand, results from obstruction of the duct of a minor salivary gland.^10,17 The obstruction may be caused by epithelial proliferation, trauma, or a sialolith.^18,19 The trapped mucus is lined by columnar or cuboidal ductal epithelium.¹⁴ Approximately 90% of mucoceles are extravasation mucoceles and the remaining 10% retention mucoceles.²⁰

Mucoceles affect patients of all ages with peak incidence in the first and second decades of life.^10,20 Both sexes are equally affected.^15,17,20 There is no racial predilection.¹⁹

Typically, a mucocele, irrespective of its etiology, presents as an asymptomatic, fluctuant, tense, well-circumscribed, dome-shaped swelling or nodule on the mucosal surface of the lip (Figures 3 and 4).^10,16,21 More than 70% of cases occur on the lower lip.²² Less commonly, the mucocele occurs on the upper lip and buccal mucosa. The size of the lesion ranges from a few millimeters to a few centimeters in diameter.¹⁸ The color ranges from deep blue to pink (the color of normal mucosa).^15,20,21 A mucocele may fluctuate in size and rupture spontaneously.¹⁹ Lesions are usually solitary but can be multiple (Figure 5).²³

Occasionally, mucoceles may occur on the floor of the mouth, soft palate, hard palate, and tongue.^12,20,22,24 The occurrence on the tongue accounts for approximately 2% of cases.²⁵ Rarely, a mucocele may arise on the ventral surface of the tongue and is known as mucocele of the gland of Blandin-Nuhn.^14,26 The glands of Blandin-Nuhn are located in the anterior ventral surface of the tongue.^14,16,20,27 These glands are arranged in a mass with a horseshoe shape and covered by thin mucous membrane.^14,16 In most cases, a mucocele of the gland of Blandin-Nuhn results from a self-inflicted bite wound.^16,27 The lesion is usually less than 1 cm in diameter. Rapid onset, fluctuation in size, bluish discoloration and fluid-filled consistency are characteristic.²⁵ A superficial mucocele, a rare subtype of the mucocele of the gland of Blandin-Nuhn, may present as a translucent fluid-filled vesicle or cyst (Figure 6).^28,29 The lesion ruptures easily and may leave a slightly painful erosion, which usually heals within a few days.

The diagnosis of oral mucoceles is mainly clinical. Depending on the size and location, a mucocele can become cosmetically unsightly.⁹ A mucocele may persist for weeks or months before it ruptures spontaneously. Recurrence is common and may lead to fibrosis.¹⁰