Introduction Lymphomas are a heterogeneous group of malignant neoplasms of lymphocytes and their precursor cells. Lymphoma is seen 3.5% of all intraoral malignancies and is the second most common neoplasm after the squamous cell carcinoma in the head and neck region. Diffuse large B-cell lymphomas (DLBCL), which is a subtype of non-Hodgkin lymphoma, are seen mostly in the paraoral region. Case presentation An 82-year-old woman was referred with a localised swelling of the mandibular buccal mucosa for 3 months. Excisional biopsy revealed the diagnosis of DLBCL in the mandible and chemotherapy regimen started immediately. However, patient died during treatment. Conclusions Non-Hodgkin's lymphomas would be late- or misdiagnosed in the perioral region that may result poor prognosis.