Palatal swelling in a young adult

Abstract

The presence of numerous minor salivary gland tissues in the posterior part of hard palate increases the possibility of salivary gland neoplasms. Minor salivary gland tumor accounts for about 15% of all the salivary gland neoplasms, of which mucoepidermoid carcinoma (MEC) accounts for about 35.9%. Although a wide range of the differential diagnosis is made by the clinicians toward a single palatal swelling without any other specific changes on inspection, a prompt “histopathological” diagnosis is of utmost importance in case of lesions like “MEC.” By taking the case study of a 23-year-old male patient who was complaining of difficulties in eating and speaking due to a swelling in the palate that was not associated with pain, etc., this case report highlights the need for an early clinical examination and prompt histopathological diagnosis of such clinically benign looking lesions, as such an action can play an ameliorating role in reducing the chances of postoperative morbidity.

INTRODUCTION

Salivary gland carcinoma constitutes 0.5% of all known malignancies and accounts for between 3% and 5% of head-and-neck cancers reported across the globe.[1,2] Due to being relatively rare neoplasms, the histopathology of salivary gland tumors are considered complex and poses challenges to diagnostic pathologists.[3] The classification carried out by the World Health Organization[4] (WHO) consists of over 40 named neoplasms, most of which show considerable amount of morphological diversity, and due to the overlapping features contained in such a classification, difficulties have been encountered in differentiating various types of tumors. There is a further hardship due to the existence of a range of nonneoplastic lesions that present themselves like tumors both clinically and histologically.[5] In such a scenario, it can be of substantial clinical value if efforts are made to identify effective early markers for the diagnosis of similar lesions.

The “mucoepidermoid carcinoma” (MEC) is one of the malignant salivary gland neoplasms involving major and minor salivary glands. The first accurate description of the MEC was attributed to Masson and Berger who summarized it as “double metaplasia epithelioma.”[6]

In the light of the above, this report deals with a case of a 23-year-old patient diagnosed histopathologically as “MEC” involving the hard palate, which presented itself as a gradual increasing swelling, persistent in nature, localized to the palatal mucosa with no secondary changes in color and or surface ulceration.

CASE REPORT

A 23-year-old male patient visited the Department of Oral Medicine and Radiology with a chief complaint of swelling in the palate for the past one month. The swelling was not associated with pain and discharge. His medical and family histories were insignificant, and the patient was apparently healthy. Extraoral examination was unremarkable. No other abnormality was found [Figure 1].

Figure 1.

Intraoral findings

Oral hygiene status of the patient was satisfactory. On intraoral examination, a dome-shaped well-demarcated swelling measuring approximately about 2 cm × 3 cm was seen on the left side posterior part of the hard palate slightly toward the midline. The swelling extended anteriorly to mesial surface of the second premolar, posteriorly to mid of the second molar, medially 2–3 mm away from the midpalatine raphae and laterally toward the gingival zone in relation to 25, 26 and 27 region. The color of the mucosa covering the swelling was similar to the normal palatal mucosa and with no secondary changes. Borders were distinct and smooth.

On palpation of the lesion, all inspectory findings were confirmed. The swelling was nontender, soft in consistency with regular smooth borders. Provisional diagnosis of a benign salivary gland tumor was made.

Occlusal radiograph of maxillary arch was taken, which showed no specific changes. Complete hemogram showed all the values within the normal range. Computed tomography (CT) was done. The CT report revealed focal erosion of the palatal cortex with lysis of the underlying bone for about 7 mm [Figure 2].

Figure 2.

Computed tomography showing bone erosion

Fine-needle aspiration cytology (FNAC) was done. The aspirate received was whitish in color and blood tinged. Smear was stained with H&E stain. The cytological findings revealed mucous droplets interspersed with inflammatory cells, and in one corner, few epithelial cells were seen with large dark nuclei and exhibiting a mild atypia. The smear also revealed the presence of few spindle-shaped cells resembling fibroblasts.

Incisional biopsy was done under local anesthesia [Figure 3] and gross specimen was submitted including 3 bits of soft tissue each measuring about 0.5 cm × 0.5 cm in size. All the specimens were histopathologically processed, and H&E staining was done. Histopathology of the specimen showed tumor composed of areas of epidermoid cells and mucous cells. The section also revealed normal salivary gland aggregates adjacent to the lesion within the submucosa [Figures 4 and 5]. The excretory ducts revealed ductal cell proliferation composing of cells resembling epidermoid cells exhibiting features of dysplasia such as nuclear and cellular pleomorphism [Figure 6]. The section also exhibited microcyst formation, areas of necrosis and focal areas of clear cell changes [Figures 7–9]. The histopathological features were not consistent with the clinical diagnosis of benign tumor of minor salivary gland.

Figure 3.

Intraoral findings – postincisional biopsy

Figure 4.

Histopathology picture showing normal salivary gland aggregates adjacent to the lesion – scanner view

Figure 5.

Histopathology picture showing mucous cells – high-power view

Figure 6.

Histopathology picture showing pleomorphic epidermoid cells – high-power view

Figure 7.

Histopathology picture showing clear cells – high-power view

Figure 9.

Histopathology picture showing numerous ductal spaces – high-power view

Figure 8.

Histopathology picture showing tumor necrosis – high-power view

The clinicopathological correlation led to a final diagnosis of MEC – low-grade type. The patient was surgically treated under general anesthesia; tumor was surgically resected by partial maxillectomy and skin grafting.

DISCUSSION

The term “mucoepidermoid tumor” was first used by Stewart, Foote and Becker in 1945. Salivary gland tumors account for 5% of the head-and-neck neoplasm with pleomorphic adenoma as the most common benign neoplasm, and MEC is the most common malignant tumor.[7] MEC is believed to arise from pluripotent reserve cells of excretory ducts that are capable of differentiating into squamous, columnar and mucous cells.[8] Most common sites for salivary gland neoplasms are the parotid glands followed by intraoral minor salivary glands. Commonly involved minor salivary glands are at the junction of the hard and soft palate, retromolar region, buccal mucosa, floor of mouth and labial mucosa in the order of frequency. The palate is the most common site for all tumors of minor salivary gland origin (55%) and more than 60% of these are malignant.[9]

Minor salivary gland tumor accounts for about 15% of all the salivary gland neoplasms, of which MEC accounts for about 35.9%. The WHO currently defines salivary MEC as “a malignant glandular epithelial neoplasm characterized by mucous, intermediate and epidermoid cells, with columnar, clear cell and oncocytoid features.”[10]

MEC occurs most frequently between the third and sixth decades of life and affects women more often than men, in a ratio of 3:2. It is frequently seen in parotid gland, followed by minor salivary glands. The involvement of minor salivary glands is commonly seen at the junction of the hard and soft palate, retromolar region, buccal mucosa, floor of mouth and labial mucosa. The palate is the most frequent site for MEC (28%), followed by the retromolar region (23%), the floor of the mouth (14%), the buccal mucosa (11%) and the lower lip (9%). Clinical presentation of MEC of hard palate is variable and depends on the grade of tumor and stage of detection.[7,10] MEC presents as several histopathological variants, such as clear cell, melanocytic, sclerosing, unicystic, sebaceous, psammomatous, spindle, goblet and oncocytic variant cells.[11]

MEC of hard palate presents as a slow-growing, persistent swelling which is usually painless and soft in consistency. Advanced disease and late diagnosis cause extensive spread, with the possibility of perforation of the hard palate and invasion into maxillary antrum or nasal cavity.

Their superficial location, intraoral tumors may appear as a blue-red tinged swelling simulating a mucocele or vascular tumor.[9] Underlying palatal or retromolar cortical bone can be eroded. The CT report revealed erosion of the underlying palatal bone. The degree of malignancy influences the interpretation of FNAC.[12] Our patient FNAC report revealed the presence of mucin droplets, large epithelial cells with dark nuclei and occasionally interspersed with inflammatory cells.

The pattern of proliferation of cells in MEC is cystic or cystic papillary. They may be graded into low, intermediate or high-grade malignancy based on five parameters: (i) proportion of cystic and solid elements, (ii) neural invasion, (iii) necrosis, (iv) anaplasia and (v) mitotic rate.[13] Our case showed proliferation of tumor cells from the excretory ducts and tumor composed of areas of epidermoid cells together with mucin-secreting cells. The epidermoid cells exhibited features of dysplasia such as nuclear and cellular pleomorphism in a stroma resembling of a thin delicate fibrovascular connective tissue including some myxoid areas. The section also exhibited areas of microcyst formation, areas of necrosis and focal areas of clear cell changes. Based on armed forces institue of pathology (AFIP) classification, our case showed 10% of necrosis and >20% of cystic component. There were no neural invasion, mitosis and anaplasia. Therefore, a total score of 3 was obtained, which confirmed our case as “low-grade MEC.”

Table 1 shows AFIP grading system for salivary MEC, and Table 2 shows AFIP grading for our case.

Table 1.

AFIP grading system for salivary mucoepidermoid carcinoma[7,10,12]

Serial number	Criteria	Points
1	Cystic component <20%	2
2	Neural invasion	2
3	Necrosis	3
4	≥4 mitoses/10 HPF	3
5	Anaplasia	4
Interpretation
1. Low grade: 0-4 points
2. Intermediate grade: 5-6 points
3. High grade: 7-14 points

AFIP: Armed forces institue of pathology

Table 2.

AFIP grading system for our case

Serial number	Criteria	Inference	Points
1	Cystic component	>20%	0
2	Neural invasion	Absent	0
3	Necrosis	Present	3
4	≥4 mitoses/10 HPF	1/10	0
5	Anaplasia	Absent	0
Interpretation
Total score: 3 - low grade (Score: 0-4)

HPF: High-power fields, AFIP: Armed forces institue of pathology

Cervical nodal metastases may be reported in MEC.[12] Our case showed no nodal metastases. MEC may also show intracranial and perineural invasion.[14] In longstanding lesions, distant metastases are reported. The most common site for distant metastases is lungs.[15] Our case showed no evidence of perineural invasion and distant metastases.

Based on the clinical, radiological and cytological examination, differential diagnosis included was pleomorphic adenoma, canalicular adenoma and mucocele, but based on the histopathological examination, all the differential diagnoses were ruled out and a final diagnosis of “MEC” was made.

CONCLUSION

Thus, clinically a palatal swelling may resemble a dental cyst, an abscess or any benign neoplasms, which leads to delay in the diagnosis and treatment. Hence, prompt clinical and histopathological diagnosis of such lesions is utmost important for successful management.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.