Malignant myoepithelioma of the maxilla posing a diagnostic dilemma
A 55-year old man reported to our department with a 4-month history of a slowly enlarging, asymptomatic mass over the right facial aspect of the maxilla and also a rapidly enlarging asymptomatic mass involving the right side of the palate, since 20 days. History of the present illness revealed that the patient had undergone extraction of the maxillary right first molar due to pain and mobility at a private clinic 4 months ago. Initially, it was associated with five episodes of nasal discharge (blood-tinged), at intervals of 4-5 days, which stopped after taking medications.\nClinically, there was diffuse swelling of the right cheek with obliteration of the right nasolabial fold. The overlying skin was intact and normal. There was neither pain nor neurologic deficit. The orbit was intact. The submandibular lymph nodes bilaterally were palpable, measuring 1 × 0.5 cm in dimension, ovoid in shape, and freely mobile. Tenderness was elicited in the right submandibular group.\nA 6 × 3 cm in size, intraoral, smooth-surfaced, submucosal swelling in the right palatal region extending from the 1st premolar to the 3rd molar, with extension into the buccal vestibule through the missing 1st molar space, obliterating it to a minimal degree, was seen []. The overlying mucosa was intact and healthy. The teeth in around the tumor mass were mobile.\nAfter clinical examination, a benign tumor of minor salivary glands, arising either from the palate or right maxillary sinus, was suspected.\nPanoramic radiography revealed a well-defined, unilocular radiolucency in the right maxilla, extending from the right maxillary 3rd molar to the right 1st premolar, causing no displacement of the roots of the teeth. The maxillary sinus was completely surrounded by intact bone except in the region of the 1st molar where a discontinuity in the sinus floor was detected. Paranasal sinus radiography revealed a well-defined, radiopaque mass in the right maxillary sinus [].\nA computed tomographic (CT) scan revealed a well-defined, well-circumscribed, encapsulated mass, involving the right maxilla, extending superiorly to the sinus roof. The mass revealed soft-tissue extensions into the palatal vault. The maxillary sinus and nasal floor were completely surrounded by intact bone, except in the region of the 1st molar, where it appeared discontinuous [].\nAn fine needle aspiration cytology of the swelling was performed. The smear showed highly cellular, cohesive clusters of epithelial cells with distinct cell borders, resembling salivary gland epithelial cells. They were round to cuboid, with distinct nuclei and nucleoli. Many spindle-shaped, myoepithelial cells were also seen scattered singly and in small clusters against a fibrillar, myxoid stromal background. A basement membrane-like, pinkish substance was also seen scattered amidst the epithelial cells. Some of the epithelial cells showed the typical acinar pattern of arrangement against a background of abundant myxoid stroma. These features were in favor of pleomorphic adenoma.\nAn intraoral incision biopsy was performed under local anesthesia. The lesion consisted of friable, hemorrhagic soft tissue. Macroscopically, the specimen measured 1.5 × 1 × 0.8 cm in dimension, was soft to firm in consistency, ovoid, and whitish to brown in color. Microscopically, a parakeratinized stratified squamous epithelium with short rete ridges, elongated spindle-shaped cells arranged in fascicles focally and few myxoid areas were noted. The subjacent connective tissue was highly cellular with dense, mixed inflammatory-cell infiltrate, plasma cells and blood vessels. Upon histopathologic findings, the diagnosis of spindle-cell tumor was interpreted.\nThe patient underwent surgical intervention under nasotracheal, hypotensive, general anesthesia. The tumor was approached via a Weber-Ferguson incision. A wide, local resection was carried out in the form of a right subtotal maxillectomy including the all teeth of the involved quardrent, preserving the infra orbital rim and posterior wall of the maxillary sinus, and the defect was resected out []. The resulting maxillary defect was reconstructed using a temporalis myofascial flap. Neck dissection was not carried out in this case.\nThe resected specimen revealed a thick, fibrous pseudocapsule, consisting of highly cellular stroma of spindle cells, plasmocytoid cells, and epitheloid cells with mitoses and lesser degree of pleomorphism. Anastomosing cords of spindle cells in a fibro-myxoid stroma were the dominant feature appreciable. In some areas, cords of cells with epithelial islands, with luminal spaces and peripheral palisading, were seen. Areas of hyalinization and chondro-myxoid differentiation were also seen [].\nThe histopathological features of the tumor proper were diagnostic of Malignant Myoepithelioma of the maxilla. Inmunohistochemical study in our case favored the diagnosis of malignant myoepithelial tumor []. Most tumor cells were strongly reactive to pancytokeratin, epithelial membrane antigen, calponin, and nuclear positivity for S-100 protein. The immunoreaction for muscle-specific actin was negative.\nDistant metastasis was ruled out by a chest radiograph, ultrasonography of the neck and abdomen, and supplemental liver function tests. To date, the case we present had no clinical or radiological evidence of loco-regional and distant metastases following surgical intervention, posing a favorable to good prognosis.