Challenging differentiation of oral malignant lymphoma from osteomyelitis of the jawbone: A case report

Malignant lymphoma (ML) of the head and neck frequently occurs in the cervical lymph nodes and Waldeyer's ring. Although ML of the maxillofacial region is rare, extranodal ML can present with symptoms similar to those of inflammation and other tumors, making diagnosis difficult. The present study describes the case of a 59-year-old female patient with ML, which was difficult to distinguish from mandibular osteomyelitis. The patient presented to Department of Oral Medicine, Hokkaido University Hospital (Sapporo, Japan) for evaluation of left cheek swelling and osteomyelitis. The X-ray examination, and contrast-enhanced CT and MRI images indicated chronic odontogenic mandibular osteomyelitis. The diagnosis of chronic osteomyelitis was pathologically confirmed by biopsy of the tooth with an apical lesion and surrounding bone, and the extraction socket demonstrated early epithelialization. However, the swelling persisted. Therefore, a second biopsy was performed, which revealed only inflammatory findings. The blood test results were unremarkable, and the diagnosis was consistent between bone scintigraphy and FDG-PET. The swelling worsened 6 months after the initial examination, and a palpable hard lump was observed in the left mandibular vestibule. A third biopsy was performed due to the presence of left facial nerve paralysis, which confirmed the diagnosis of diffuse large B-cell lymphoma. The patient was treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone. The soft tissue thickening and cheek swelling were resolved, and the patient achieved remission. In the present case, the diagnosis was challenging due to the presence of chronic mandibular osteomyelitis derived from periapical periodontitis and extranodal marginal lymphoma of the mandible. Establishing a diagnosis of ML by biopsy can be complex, and considering the possibility of ML when managing unusual and persistent facial swelling is important.