A case of spontaneous regression of lymphoma in the mandibular gingiva after biopsy

•A mass that developed on the mandibular gingiva confirmed a pathologic diagnosis of a diffuse large B-cell lymphoma.•This high-grade lymphoma spontaneously regressed after biopsy.•Spontaneous regression of high-grade lymphomas in the oral cavity is of special interest and very few such cases have been reported.

We report a case of lymphoma that developed on the mandibular gingiva and spontaneously regressed after biopsy was performed. The patient was an 87-year-old man who visited our hospital with a complaint of gingival swelling in the left mandibular molar region. We observed an elastic, soft, well-demarcated, granuloma-like mass measuring 30 × 25 mm in size and comprising partially white pseudomembranous areas. We conducted a biopsy, which confirmed a pathologic diagnosis of a diffuse large B-cell lymphoma. Because of age constraints, the patient was monitored without being administered aggressive therapy, and the mass disappeared 20 days after biopsy. We then performed a follow-up biopsy, which revealed the absence of tumor cells. There was no recurrence of lymphoma during the 2.5-year follow-up period.