Mucoepidermoid Carcinoma of Minor Salivary Gland in a Patient with Asymptomatic Palatal Swelling - A Case Report.

Incidence of abundant minor salivary gland tissues in the posterior part of hard palate surges the likelihood of salivary gland neoplasm especially in this part of the oral cavity. Minor salivary gland tumor accounts for virtually 15% of all the salivary gland neoplasm, wherein mucoepidermoid carcinoma comprises of 35.9%. Current paper reports a case of mucoepidermoid carcinoma of the posterior part of the hard palate which was an incidental finding. It presented as well-defined smooth swelling, the preliminary radiographic investigation revealed no appreciable bony changes and offered an impression of a benign tumor. Histopathological investigation displayed features of mucoepidermoid carcinoma of intermediate grade. The lesion was surgically excised and the patient was under regular follow up for 3years. The paper focus on the magnitude of swift clinical diagnosis of specific lesions, so increasing the survival rate and reducing the morbidity. Copyright:

INTRODUCTION

Mucoepidermoid carcinoma (MEC) is a malignant epithelial tumor that stems from pluripotent cells in the salivary gland epithelium's excretory channels.[1] Massao and Berger were the first to describe it in 1924. Salivary MEC is at this time defined as “a malignant glandular epithelial neoplasm characterized by mucous, intermediate, and epidermoid cells, with columnar, clear cell, and oncocytoid characteristics,” according to the World Health Organization (WHO).[2] When tumors of salivary gland are considered, MEC accounts for less than 10%. But among the malignant variety, it constitutes roughly 30% of all malignant tumors of salivary glands. MEC has been shown to occur in a 3:2.4 ratio among females during the third and sixth decades of life. The parotid gland is the most common site, followed by minor salivary glands. The palate (28%) is the utmost common site for MEC, followed by the retromolar region (23%), the floor of the mouth (14%), the buccal mucosa (11%), along with the lower lip (9%). MEC of the hard palate presents in a variety of ways, depending on the tumor's grade and stage of discovery.[3] Central MEC of the mandible is also reported.[4] MEC of the hard palate can appear as a slow growth, and because it is asymptomatic, its existence is only discovered after several years.[5] We present a case of palatal swelling in a 25-year-old Saudi woman who exhibited pain in the left lower back tooth region as her main complaint. This research emphasises the need of a comprehensive intraoral examination and a complete case history in detecting a dangerous condition early.

CASE REPORT

A 25-year-old female patient reported to the diagnosis clinic with a chief complaint of pain in lower left back tooth region for a month. The pain was moderate, and was getting aggravated on cold and hot food intake and was relieved on taking analgesic. There was no other relevant medical, personal, or family history. The patient had undergone orthodontic treatment and was wearing a retainer for 2 years. There was no abnormality on general physical examination and extraoral examination. On intraoral examination, it was found that there was a solitary bluish pink swelling at the posterior edge of a maxillary acrylic denture plate. The swelling was approximately 3 × 2.5 cm in the posterolateral aspect of the hard palate in the region of teeth number 26 and 27. Anteroposteriorly, it was extending from the mesial aspect of teeth number 26 to the distal aspect of teeth number 27. Medially, the swelling extended approximately 3 mm lateral to the midpalatine raphe. Laterally, the swelling extended around 0.5 cm lateral to the palatal gingival margin of teeth number 26 and 27. It was well defined with normal overlying mucosa; there was no ulceration or other surface changes. On palpation, it was soft to firm in consistency, nontender and fluctuant at the center with no observable blanching or pulsation [Figure 1a]. The patient was aware of this swelling and according to her, it was of sudden onset and its size was the same since she noticed it from a month, it was totally asymptomatic with no pain or discomfort. No other abnormality was detected in the adjacent teeth or periodontium. Panoramic radiograph showed a periapical lesion in relation to teeth number 36 and 46. Maxillary sinus floor was intact with no other changes [Figure 1b]. Intraoral periapical radiograph in relation to teeth number 26–28 [Figure 1c] and occlusal radiograph of maxilla did not show any appreciable changes [Figure 1d]. On the basis of the clinical and radiographic features, provisional diagnosis of benign minor salivary gland tumor was specified, considering mucocele, pyogenic granuloma, and vascular lesion in addition to malignant minor salivary gland tumor in the differential diagnosis. Fine-needle aspiration showed thin blood-like fluid [Figure 2a] with collapsing of the entire lesion, and the lesion soon refilled again to form a dome-shaped smooth swelling within the next 1 h. The aspirate was sent for histopathologic examination, which gave the impression as pleomorphic adenoma. Computerized tomography (CT) was advised and there was no detectable bony involvement [Figure 2b and c]. Following CT, incisional biopsy of the lesion was planned and performed. Microscopically, tissue section showed fragments of tissue covered by stratified squamous epithelium; the underlying stroma showed an infiltration of tumor composed of three types of cells, intermediate, mucinous, and squamous. Extracellular mucin was noted with infrequent mitotic figures [Figure 3a and b]. Immunohistochemistry showed CD5/6, which was focally positive mostly in the squamous component, and CK7, which was focally positive mostly in the acinar component was seen. Based on the histological features, MEC of an intermediate grade was considered as the final diagnosis. Wide local excision of the lesion was planned and performed; there were no postoperative complications. The patient is further kept on regular follow-up for 3 years [Figure 3c].

Figure 1

(a) Solitary swelling at the left posterior maxilla. (b) Panoramic radiograph showing periapical lesion in relation to teeth number 36 and 46 with no other changes. (c) Intraoral periapical radiograph in relation to teeth number 26–28. (d) Occlusal radiograph of maxilla

Figure 2

(a) Fine-needle aspiration shows thin blood-like fluid. (b and c) Coronal and axial sections of CT. CT = computerized tomography

Figure 3

(a and b) Histopathologic images with H and E staining at magnification 5× and 10×. (c) Postoperative follow-up after 3 years. H&E = hematoxylin and eosin

DISCUSSION

MEC of the hard palate exhibits as a slow-growing, persistent, asymptomatic soft swelling. However, when secondarily infected, pain and pus discharge may be present. Advanced disease can present with ulceration, induration/firm mass, resorption of the underlying bone, tooth mobility, and root resorption; and as the lesion left untreated can cause perforation of the hard palate and invasion into maxillary antrum or else nasal cavity.[6] The cause of MEC is unknown, but past ionizing radiation exposure could be a factor, as cases of MEC have been described following radiation therapy for thyroid cancer or leukemia. While most other head and neck cancers are linked to smoking and drinking, the salivary gland tumor is not one of them.[7] Local trauma is also considered in the development.[58] MEC on the palate can be difficult to distinguish from all benign and malignant tumors of the hard palate, which include pleomorphic adenoma, polymorphous low-grade adenocarcinoma, adenoid cystic carcinoma, and squamous cell carcinoma, MECs arises from intraoral minor salivary glands of low to moderate grade, according to Moraes et al., can be handled by extensive local surgical excision with tumor-free surgical margins. The tumor should be dissected down to the periosteum if there is no sign of bone involvement. If there is any sign of periosteal engrossment or bone involvement, the affected bone should be removed. For high-grade tumors, a more aggressive surgical treatment with postoperative radiation and chemotherapy may be necessary.[91011] MECs of low and intermediate grade have an indolent clinical course, and metastasis is uncommon. If there is clinical indication of metastases, a radial neck dissection is recommended. The prognosis is determined by the tumor's grade and stage.[12] Cervical nodal metastases may be reported in MEC.[9] Our case showed no nodal metastases. The lung is the most commonly involved site of distant metastasis.[13] In the present case, the patient had completely ignored the presence of this small lesion and it could have gone unnoticed as the patient was wearing the appliance. Patient reported to us for the treatment of chronic tooth pain, and a case of malignancy was revealed due to the comprehensive diagnostic procedure.

CONCLUSION

Dental practitioners may be the first health-care providers to examine patients exhibiting palatal lesions. This paper highlights the importance of systematic case history and clinical examination, which led to the diagnosis of a case with MEC. It was an incidental finding, and as it was totally asymptomatic, the patient had completely ignored the existence of it. Delay in diagnosis of the lesion in its early stage can leads to spread to adjacent vital structures, requiring more extensive surgery which affects the quality of life and postoperative morbidity.

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Conflicts of interest

There are no conflicts of interest.