Abstract: Peripheral myxoma arising in soft tissues such as the gingiva is a rare entity. This article reported a case of peripheral myxoma of the right maxillary gingiva in a 74-year-old female patient who presented with a painless pedunculated mass on the buccal gingiva adjacent to the right maxillary teeth 14 to 16 for more than one year. Imaging examinations revealed no jaw bone destruction. Wide local excision under general anesthesia was performed, along with curettage of the bony surface and grinding with an ultrasonic bone knife. Hematoxylin-eosin (HE) staining showed scattered spindle/stellate cells in an abundant myxoid stroma with mild atypia, rare mitoses, and a focal mild inflammatory cell infiltrate; no definite odontogenic epithelial components were identified. Immunohistochemical staining demonstrated positive Vimentin expression, focal positive SMA expression, negative CK expression, and a Ki-67 proliferation index of approximately 20%. Peripheral myxoma needed to be differentiated from peripheral odontogenic myxoma (POM) and epulis with myxoid degeneration. This case suggested that the origin of gingival myxoid masses should be determined with caution. For lesions without bone invasion, adequate soft tissue excision combined with bony surface curettage and long-term follow-up are recommended to reduce the risk of recurrence.

Key words: Myxoma, Peripheral myxoma, Gingival mass