口蓋に発生した筋上皮腫の１例

Abstract

Myoepithelioma is a rare tumor (incidence less than 1 % of all salivary gland tumors). We report a case of myoepithelioma of the hard palate.A 15-year-old man complained of a painless mass on the palate. There was a wellcircumscribed swelling, measuring 25mm in diameter, on the hard palate. It was dark blue and had an elastic soft consistency. Sagittal magnetic resonance images revealed on oval mass with iso-intensity on T 1-weighted images and medium high intensity on T 2-weighted images. The mass pressed the hard palate toward the nasal cavity, but a sheet of bone intervened between the mass and the nasal floor. The preoperative histopathological diagnosis, based on examination of an incisional biopsy specimen, was monomorphic adenoma.With the patient under general anesthesia, the tumor was removed subperiosteally with a 5-mm safety margin of mucosa. The osseous palate was hollow, but there was no bone destruction. It was therefore not resected. The tumor was 20mm in diameter and surrounded by a thin fibrous membrane.Microscopically, the tumor consisted of plasmacytoid and spindle-shaped cells with round eccentric nuclei surrounded by abundant homogenous eosinophilic cytoplasm in a fibrous stroma.Immunohistochemical studies revealed positive reactions for cytokeratin, vimentin, and S100 protein in the tumor cells.Finally, the postoperative histopathological diagnosis was myoepithelioma (combination of plasmacytoid and spindle-shaped cells).Wound healing was good, and there was no evidence of recurrence as of 3 years after the operation.