Mucoceles are the most common lesion of oral mucosa, presenting as a benign lesion involving the minor salivary glands. They commonly occur in the labial mucosa, particularly the lower lip, and are frequently diagnosed in young individuals.¹ Histologically, mucoceles can have two different presentations: (1) a pseudocyst (extravasation mucocele) due to a traumatic disruption of a salivary gland duct that results in secretion of saliva into the surrounding tissues; or (2) a mucous retention cyst resulting from blockage of salivary flow, most likely due to a sialolith.^1-3 Clinically, the pseudocyst and mucous retention cyst look similar; the differentiation is seen in the histology. For both, excisional biopsy for the purpose of diagnosis also becomes the most effective treatment, with a low rate of recurrence in either case.²

A mucocele commonly presents as a solitary, well-delineated, dome-shaped lesion involving the inner surface of the lower lip, buccal mucosa, ventral tongue, or floor of the mouth. A mucocele in the floor of the mouth, when associated with the sublingual gland, is referred to as a ranula and is relatively rare.³

The current case report is unusual in two respects. First, the patient presented with three lesions of the lower lip, which appeared as mucosa-colored nodular lesions and were consistent with a clinical diagnosis of mucocele or irritation fibroma (Figure 1). A search of the literature using PubMed and Ovid Medline search engines confirmed the unusual nature of this case, as only one reported case of multiple mucoceles was located.⁴ Second, all three lesions were firm on palpation and exhibited some degree of hyperkeratosis, making the differential of mucocele versus irritation fibroma difficult without a biopsy for histologic diagnosis. (Author's note: The University of Missouri-Kansas City [UMKC] institutional review board [IRB] determined that a case report is not considered human subjects research and, thus, is outside the purview of an IRB. Further, because no patient identifying information is included in this report the privacy rule does not apply.)

Case Report

A 9-year-old African American female patient was referred to the Pediatric Dentistry Department, UMKC School of Dentistry from a private practice for "bumps on lower lip." The patient was then referred to the school's Advanced Education in Periodontics clinic for examination and biopsy. There were three lesions, identical in presentation except for size. They had been present for 2.5 months. The patient, who was cooperative, stated that the lesions "got bigger when I bite on them and are very annoying." Clinical examination revealed three mucosal lesions on the inner surface of the lower lip, with diameters of approximately 7 mm, 5 mm, and 3 mm. All three lesions showed clinical evidence of hyperkeratosis and were firm to palpation (Figure 1).

The guardian reported the patient was medicated with clonidine 0.1 mg, once a day, for post-traumatic stress disorder (PTSD). The patient was not receiving psychological counseling, and the guardian was reluctant to discuss family history. Consequently, nothing was known regarding the reason for and duration of PTSD.

Treatment was rendered during a subsequent appointment that included nitrous oxide sedation, local anesthesia, and excisional biopsy of all three lesions utilizing a scalpel incision. The excised lesions were submitted to pathology for histologic analysis. Sites were closed with 5-0 chromic gut sutures (Figure 2). Postoperative instructions were given, which included the use of ibuprofen for post-surgery discomfort. The patient was unavailable for an immediate postoperative visit but was contacted 3 months later and provided a follow-up photograph showing complete healing of the three biopsy sites (Figure 3).

The guardian signed a consent on behalf of the patient for treatment and consented to publication of patient information and images should a case report publication be pursued.

The histopathologic findings showed extravasation of mucin into the surrounding fibrovascular connective tissue, originating from a severed salivary duct, forming a cyst-like area (Figure 4). The effusion of mucin elicited a reactive inflammatory response, resulting in granulation tissue and an influx of macrophages (Figure 5) to engulf the spilled mucin (ie, foamy histiocytes). The adjacent minor salivary glands exhibited a chronic inflammatory cell infiltrate and dilated ducts. The overlying oral epithelium was hyperkeratinized due to repeated episodes of biting trauma (Figure 6). For all three lesions, the diagnosis was mucocele, extravasation type.

Discussion

In cases such as this, differential diagnosis should include mucocele, irritation fibroma, salivary gland neoplasm, vascular malformation, lipoma, and neurofibroma.³ As stated previously, the clinical characteristics of a mucocele include a dome-shaped swelling, fluctuant to firm upon palpation, and common to the lower lip.¹ Differentiation between a fibroma and mucocele can be a difficult visual diagnosis because they may be similar in size and shape, and both may present with a hyperkeratotic surface, or not (Figure 7 and Figure 8). Consequently, both lesions require biopsy to confirm the clinical impression.

Clinically, lip biting may present as a simple hyperkeratotic lesion on the vermillion border, an irritation fibroma, or a mucocele. These lesions commonly present as a single entity, and multiple lesions are rarely encountered.³ While not specifically listed in the 2022 edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR),⁵ persistent lip biting falls under "other specified obsessive-compulsive and related disorders." More specifically, persistent lip biting is a form of body-focused repetitive behavior (BFRB)."⁶

BFRBs constitute a group of detrimental behaviors directed toward the body, including hair pulling (trichotillomania), skin picking or cutting (dermatillomania), nail biting, and, as in the present case, persistent lip biting. BFRBs are repetitive and voluntary,⁶ but the affected individual often reports a loss of control over the behavior.⁷ The urge to perform BFRB is often triggered by stimuli or situations.

Emotional and physical trauma, such as violence, abuse, or neglect, are strongly related to PTSD in children and adolescents. The most common comorbidities with PTSD include attention deficit hyperactivity disorder, depression, and anxiety.⁸ In the present case, stress and anxiety due to PTSD were the most likely stimuli that initiated the persistent lip biting.

BFRB patients respond favorably to cognitive behavioral therapy (CBT).⁹ Other forms of behavioral therapy that have been used to treat BFRB include habit reversal training and dialectical behavioral training. Indeed, it has been suggested that trauma-focused CBT is more effective for most children and adolescents with PTSD than the use of medications.^10,11 The combination of CBT and medication is commonly reserved for severe cases of PTSD.¹⁰ In the present case, the patient was prescribed 0.1 mg per day of clonidine alone. Due to the patient's guardian's reticence in providing a complete family and treatment history, it remained unclear why clonidine alone, without psychotherapy, was selected as the primary treatment for PTSD. It should be noted, however, that clonidine, an alpha-2 adrenergic agonist, reduces the release of norepinephrine and has been used as a treatment for PTSD.^12,13

In the present case, by removing the entire lesion, the excisional biopsy also became the definitive treatment. Other methods for mucocele removal have been reported and include carbon dioxide (CO₂) laser, cryosurgery, intralesional steroid injection, and sclerosing agents.^14-16 It should be noted that the recurrence rate is comparatively high for mucoceles and low for irritation fibromas.¹⁷ The psychological component of the etiology must be addressed to ensure a positive long-term outcome, including referral to an appropriate mental health professional.

Conclusion

This case presentation was unusual in that the patient presented with multiple, concomitant mucoceles on the lower lip with an etiology of lip biting related to PTSD. Definitive management of such a case should include excisional biopsy for differentiation and diagnosis and an appropriate referral to a mental health provider for assessment and management of PTSD.

Acknowledgment

The authors thank Eileen Cocjin, DDS, and student doctor Fatema Behbahani, DDS, for their collaboration and referral of the patient to the University of Missouri-Kansas City Advanced Education in Periodontics Program.

About the Authors

Therin J. Baum, DDS, MS
Private Practice in Periodontics and Implantology, Kalispell, Montana

Simon R. MacNeill, BDS, DDS
Professor, Department of Periodontics, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri

Patrick Lai, DDS, MS, PhD
Associate Professor and Director, Advanced Education in Periodontics Program, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri

Tanya M. Gibson, DDS
Associate Professor, Department of Oral and Maxillofacial Pathology, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri

Christopher M. Cobb, LPC
Private Practice in Psychology, Lee's Summit, Missouri

Charles M. Cobb, DDS, MS, PhD
Professor Emeritus, Department of Periodontics, School of Dentistry, University of Missouri-Kansas City, Kansas City, Missouri

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