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Diagnosing a Rare Intraoral Lesion

This case study will help you identify this type of oral pathology using clinical, radiographic, and histologic findings.

This case report details the process leading to the diagnosis of a rare intraoral lesion. Relevant clinical, radiographic, and histologic findings of this lesion are included along with a discussion to help dental practitioners identify and diagnose this type of lesions in their practice.

A 40-year-old, healthy woman presented to a university dental clinic for her routine recare visit in February 2022. Her prescription medications included rizatriptan for migraines and fluconazole as needed for yeast infections. She reported a history of cigarette smoking for more than 20 years, but had quit about 4 years ago.

During examination at this recare visit, a localized, raised, asymmetrical area of erythema and edema measuring 9 x 14 mm located in the left retromolar pad area was detected. The patient reported no intraoral symptoms, but stated she has been experiencing a “swelling of her gums in the lower left area” accompanied by pain “inside her left ear for about a day.”

This lesion was not present at her previous recare visit in October 2021. In light of this discovery, efforts were made to begin gathering baseline diagnostics and measurements to determine the source of the lesion. A panoramic radiograph was taken (Figure 1) to investigate the potential etiology of her ear pain symptoms and to view the area around retromolar pad clinical findings. In addition, tooth #18 was thoroughly debrided to rule out food impaction as a source of the retromolar pad erythema and edema. To alleviate symptoms, the patient was prescribed amoxicillin (875 mg)-clavulanic acid (125 mg) every 12 hours for 7 days and scheduled for a follow-up examination.

During the follow-up evaluation of the retromolar pad area in March 2022, there was no change in its clinical presentation (size, color, consistency). A localized, pronounced area of erythema and edema measuring 9 x 14 mm remained in the left retromolar pad area. With no improvement or resolution of the lesion, the patient was promptly referred to the oral surgery faculty for an evaluation and an incisional biopsy was recommended. Patient declined to proceed with the recommended biopsy.

One month later at her recare visit in April 2022, the patient complained of overnight pain in this area that woke her up at night. The patient returned for an evaluation. Clinical examination revealed that the dimension of the lesion had remained relatively the same and remained painless to the touch with the exception that it had now extended onto the left buccal mucosa (Figure 2).

With the development of overnight pain, the patient became motivated to proceed with the biopsy. Due to the prominent swelling exhibited by the lesion, upon complete resection of the lesion, only a 5×5 mm specimen was obtained and submitted for pathology services (Figures 3 and 4).

A diagnosis of mucoepidermoid carcinoma (MC) with evidence of malignancy was made. The patient was referred to an otolaryngologist for further evaluation and definitive care. Upon returning for a recare visit in August 2022, the patient reported that she was treated by a medical surgeon who performed a more definitive resection of the lesion and is closely monitoring it for signs of recurrence.

MC lesions were originally labeled as mucoepidermoid tumors due to their variable biologic potential.1 Histologically, MC tumors present as mixed squamous and mucus-secreting cells that may organize to form cords, sheets, or cystic configurations.2 Benign lesions typically display a regular pattern, whereas malignant lesions often present with an irregular (ie, anaplastic) arrangement.

Low-grade tumors consist largely of mucous-secreting cells. In contrast, high-grade tumors are dominated by squamous cells with a paucity of mucus-secreting cells. A greater emphasis on performing oral cancer screening during routine dental visits has led to an increase in the identification of MC. It has also yielded growing evidence that low-grade (benign) tumors often possess the potential for malignant transformation. Histologically, MC cell types are classified as low-, intermediate-, and high-grade.

More than a dozen known types of malignant salivary gland tumors exist. MC is one of the most common intraoral malignant neoplasms of the salivary glands3 and represents approximately 10% to 15% of all salivary gland tumors.2,4 Risk factors include (but are not limited to) tobacco and alcohol use, radiation exposure, and exposure to environmental toxins.

The etiology of MC tumors manifests over a wide age range (15 to 86 ) with a slight predilection for women.5 They present as asymptomatic, firm, dome-shaped swellings and are observed more frequently in the palate than any other areas.3,4 Albeit rare, MC tumors have been identified in the mandible of pediatric patients.6 This makes this retromolar lesion of an adult an atypical finding.

Diagnosis of MC is achieved through an incisional or excisional biopsy of the lesion followed by hematoxylin and eosin staining for histopathologic analysis. Although a needle biopsy method can be done, there have been reports of misdiagnosis resulting from this approach.7

Treatment for MC typically involves adequate excision of the tumor. In cases where the tumor presents with unclear margins, radiation therapy has shown to yield improved outcomes as a supplement to surgery.8 Limited studies have been conducted on the effects of systemic therapy (chemotherapy, monoclonal antibodies, or targeted therapy).4,9 Prognosis depends on the tumor’s grade level. MC tumors rarely exhibit signs of metastasis and are more amenable to cure via surgery. Similar to other neoplasms, low- or intermediate-grade tumors show more favorable long-term survival rates compared to high-grade tumors.

Upon identification of rapid onset swelling in the retromolar pad areas, the dental practitioner should strongly recommend an incisional biopsy to ascertain a diagnosis. Once a diagnosis of malignancy is confirmed, prompt referral to a head and neck surgeon for evaluation and treatment is appropriate.


The author would like to thank to Hargrow Barber, DDS, and Douglas Beals, DDS, MS, for their assistance with this manuscript.


  1. Neville BW, Damm D, Allen CM, Chi AC. Oral and Maxillofacial Pathology. 4th ed. Philadelphia: Elsevier; 2009.
  2. Langlais RP, Miller CS, Nield-Gehrig JS. Color Atlas of Common Oral Diseases. 4th ed. Philadelphia: Wolters Kluwer; 2009.
  3. Sama S, Komiya T, Guddati AK. Advances in the treatment of mucoepidermoid carcinoma. World J Oncol. 2022;13:1-7.
  4. Kumar V, Abbas AK, eds. Robbins Pathologic Basis of Disease. 6th ed. Philadelphia: WB Saunders Co; 1999.
  5. Rapidis AD, Givalos N, Gakiopoulou H, et al. Mucoepidermoid carcinoma of the salivary glands. Review of the literature and clinicopathological analysis of 18 patients. Oral Oncol. 2007;43:130-136.
  6. Kahn MA, Lucas RM. Mucoepidermoid tumor: a case report involving the operculum of an erupting permanent second molar. Oral Surg Oral Med Oral Pathol. 1989;68:375-379.
  7. Gotoh S, Nakasone T, Matayoshi A, et al. Mucoepidermoid carcinoma of the anterior lingual salivary gland: a rare case report. Mol Clin Oncol. 2022;16:1-5.
  8. Brandwein MS, Ivanov K, Wallace DI, et al. Mucoepidermoid carcinoma: a clinicopathologic study of 80 patients with special reference to histological grading. Am J Surg Pathol. 2001;25:835-845.
  9. McHugh CH, Roberts DB, El-Naggar AK, et al. Prognostic factors in mucoepidermoid carcinoma of the salivary glands. Cancer. 2012;118:3928-3936.

From Dimensions of Dental Hygiene. June/July 2024; 22(4):20-21

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