Paediatric mucoepidermoid carcinoma of palate: Literature review and report of a case

Mucoepidermoid Carcinoma (MEC) is the most common malignant tumor in salivary glands. About 70% of these tumors are found in the parotid gland, 15 to 20% in the oral cavity, mostly in the palate, and 6 to 10% in the submandibular gland. MEC has female predilection and the mean age at onset is in the 5th decade of life. The treatment decision depends on the histopathology (Low-grade, Intermediate-grade, High-grade). A 12 year-old male with a right palatal tumor, having no association with vital teeth arrived at our service centre. The excisional biopsy reported was: MEC Intermediate-grade. Because few cases of MEC in Paediatric patients have been reported, a review of the literature, with range of age 0-17 years, was made, 24 patients with diagnosis of MEC in Palate, included our case, were found, the average age was 14 (29%), the predilection in genre was female with 19 cases (79%), and 5 cases in Male (21%). MEC has a female predilection and is uncommon in the first decade of life but should be considered even in paediatric patients. The prognosis depends on the clinical stage, grade of the tumor, location, and adequacy of treatment. The presence of nodal disease and distant metastases implies a poor prognosis.


INTRODUCTION
Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor, statical data indicate that it is the most common parotid malignancy (89%) and that is the most common malignant salivary gland tumor in children.About 70% of MEC are found in parotid gland, 15-20% in oral cavity, mostly in the palate, and 6 to 10% in submandibular gland.MEC has female predilection 3:1 at fifth decade of life (Marx and Stern, 2012).MEC was originally described by Volkmann in 1895 (Bhat et al., 2014), the oral cancer foundation refers that MEC was *Corresponding author.E-mail: cesarvi@att.net.mx.Tel: 045-8183629904.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License described by Masson andBerger in 1924 andin 1945 Stewart recognized MEC of salivary glands as a separate entity among salivary neoplasm (Ranganath et al, 2011).
Treatment decisions are based on histologic grading.The grading of MEC depends on the mix of cell types.Low grade is characterized by well-form cyst that contains mucin, lined by a mixture of mucos, intermediate and epidermoid cells.Intermediate grade contains smaller and fewer cyst and have more solid appearance, consist of intermediate cells, epidermoid cells, and some mucous cells.
High grade are solid and consist of intermediate and epidermoid cells, which show considerable atypia and mitotic activity is present (Marx and Stern, 2012).A review of literature about MEC of Palate revealed 24 documented cases in paediatric patients, included a case reported by our service of Oral and Maxillofacial Surgery at School of Dentistry of Universidad Autónoma de Nuevo León, México.

Case presentation
A Twelve-years-old Male arrived to our service; a complete anamnesis was made, the patient does not have antecedents or family cancer history, the only relevant antecedent was previous dental injury in anterior-inferior teeth 6 years before.He refers began with a mass in Right Palate five months previous (May, 2015), which was detected by his dentist, biopsy by puncture was practice that time without specific diagnosis.
At clinical examination was made, with oval face, esqueletal class III, abscense of inferior anterior theet, tongue and the rest of tissue had normal characteristics, a mass in the right hard palate, 2 cm in size was observed, with blue/red color, diffuse borders, fluctuant, and sesil base, the cervical palpation does not reveal lymph nodes (Figure 1).A Cone Beam was taken, without any bone involvement.An Incisional Biopsy was made (October, 2015), because the characteristics of clinical presentation, it was made superficial and the histopathology report us normal tissue.It was decided to excisional biopsy with a scalpel No. 15, removing the entire lesion 0.5 mm around, hemostasis was made with electrocautery, and an obturator for the defect of tissue was used.
The histopathologic analysis, made with hematoxilyneand-eosin by the Pathology Department, reported presence of quistic sppaces covered by epidermoid cells and mucus secreting cells.Filling these spaces are nests and diffuse layers of these same cells between a fibrous connective tissue, which correspond to MEC of intermediate grade (Figure 2).The patient actually, 9 months after, has no evidence of lesion; a new Cone beam was taken, with no evidence of bone involvement.An oncological review was conducted by the specialist Garcia et al. 55 with no evidence of tumor.

RESULTS
The literature review include search in Pub Med, JOMS and IJOMS, the range of age was 0 to 17 years, 24 patients with diagnosis of MEC in Palate, including our case, were found.The youngest age was 5 years; 1 case (4%), the oldest 17 years old; 3 cases (13%), the average of age was 14 (29%).The predilection of genre was female with 19 cases (79%), and 5 cases in Male (21%) (Table 1).The most common location was hard palate; 17 cases (71%), followed by junction of hard and soft palate; 4 cases (17%), and 3 cases of soft palate (12%).The time of evolution was not specified in almost all the cases, but 1 year (9%) and 1 month (9%) was the most common.The size was not specified in almost all the cases 13 (54%) and 3 patients reported 2 cm (13%) (Table 1).One case reported bone involvement and another reported erosion of bone.Concerning the Histologic grade: low grade was the most prevalent with 22 cases (92%) of the total, 1 intermediate (4%) and 1 was not specified (4%).The common treatment was excision.One case had recurrence on 5 years follow up (Table 1).

DISCUSSION
The firm attachment of the mucosa of hard palate to the underlying periosteum, the anatomic proximity of the mucosa to the bone, and the abundance of minor salivary glands make the hard palate a unique anatomic region.Within this context, neoplastic lesions of the hard palate may show different characteristics and different histopathologic compositions compared with other anatomic regions.(Aydil et al., 2014).MEC is actually an uncommon tumor in minor glands in child.About 1% -5% of all salivary glands tumors develop in children and adolescents, and the MEC are the most common malignancy.(Ritwik et al., 2012).In 1987 only 17 cases of MEC of the palate in children had been published.(Gustafsson et al., 1987).Although this salivary gland tumor represents a rare oral lesión in children, it should be considered when a lesion has a similar appearance as a mucocele but is found at a site other than the lower labial mucosa.(Flaitz, 2000).The mucocele is a common, reactive lesion of salivary glands that is seen frequently in children.This lesion presents as a dome shaped, translucent blue swelling that is fluid-filled.(Flaitz, 2000).Few series of cases describing salivary gland tumors in the pediatric population have been published.This Case represent an additional case of a Intermediate-grade MEC of the palate of a 12 years old child.Here, the average of age was 14 (29%), the predilection of genre was female with 19 cases (79%),