Mucoepidermoid carcinoma of the base of the tongue: a case report and review of the literature

Abstract

Background: Mucoepidermoid carcinoma originates from reserve cells present in ducts of salivary glands and is the most common malignancy of the salivary glands. It is commonly found in the parotid gland, followed by the palatal and buccal mucous membranes. However, mucoepidermoid carcinoma occurrence in other intraoral sites, including the tongue base, is extremely rare.

Case presentation: A 33-year-old Chinese man presented with a progressively enlarging mass at the base of his left tongue. Contrast-enhanced computed tomography and magnetic resonance imaging revealed an augmented soft tissue mass in the left jaw region with indistinct boundaries, enlargement of cervical lymph node of uncertain etiology, and no evidence of distant metastasis. A transoral needle biopsy from the mass pathologically revealed low-grade mucoepidermoid carcinoma. Complete transoral excision and cervical lymph node dissection were performed, followed by reconstruction with an anterolateral thigh free flap. Examination of the obtained surgical specimen confirmed low-grade mucoepidermoid carcinoma with MAML2 gene fusion in the base of the tongue. The tumor was removed with negative margins, and the cervical lymph nodes were free of disease. The patient had an uneventful recovery and showed no evidence of recurrence or metastasis at 40 months of follow-up.

Conclusion: We present a rare case of mucoepidermoid carcinoma at the base of the tongue. Furthermore, we review related literature and discuss its clinical features, histopathological characteristics, and treatment strategies.

Keywords: MAML2 rearrangement; Mucoepidermoid carcinoma; Reconstruction; The base of tongue.

Fig. 1

Intraoral photograph showing an ill-defined mass on left lateral border of tongue, crossing the midline, covered with ulcerated lesion

Fig. 2

Preoperative axial computed tomography (A) and MRI (B) scan showing a 4.5 × 3.0 × 3.1 cm soft tissue mass at the base of the left tongue that infiltrated the muscle and involved the whole thickness of the tongue

Fig. 3

Intraoperative photograph. A Intraoperative image of complete transoral excision and bilateral cervical lymph node dissection involving left levels I–IV and right levels I–III; B the close view of excised specimen; C a left anterolateral thigh free flap was harvested for defect reconstruction; D final intraoperative reconstructive appearance

Fig. 4

Pathological and molecular analysis revealed a low-grade MEC in the base of the tongue. A Hematoxylin and eosin staining showed proliferation of the tumor specimen with cystic dilatation full of mucus cells (magnification, ×100); B immunohistochemistry demonstrating positivity for tumor protein 63 (magnification, ×100); C immunohistochemistry demonstrating positivity for cytokeratin 7 (magnification, ×100); D periodic acid–Schiff staining demonstrating positive mucous cells and the contents of microcystic spaces (magnification, ×100); E fluorescent in situ hybridization confirming the presence of MAML2 rearrangement where the green probe and red probe are split

Fig. 5

Physical examination and imaging scans of the patient at 9-month follow-up showed no evidence of recurrence. A, B Postoperative photograph demonstrating well-healed reconstructed site; computed tomography (C) and magnetic resonance imaging (D) scan did not show any evidence of recurrence in 9 months postoperative

Fig. 6

Imaging scans of the patient at 40-month of follow up showed no evidence of recurrence. Computed tomography (A) and magnetic resonance imaging (B) scans did not show any evidence of recurrence at 40 months postoperative