Lymphoma, which accounts for 3.5% of all oral cancers, is further divided into Hodgkin's lymphoma (HL) and non-Hodgkin's lymphoma (NHL). NHL accounts for 96% of lymphomas, and diffuse large B-cell lymphoma (DLBCL) is the most common subtype accounting for 32% of NHL. In the oral cavity, extra-nodal non-Hodgkin's lymphoma may develop in the dentoalveolar region of the maxilla or mandible. It can also mimic inflammatory lesions that occur around periodontal tissues, such as periapical granuloma and chronic osteomyelitis. Misdiagnosis of jaw lymphoma can delay appropriate treatments and worsen the prognosis. Therefore, to avoid delay in diagnosis, clinicians should identify the possible malignancy based on unusual symptoms, clinical findings, radiographic examinations, and histopathological evaluation. We present two cases of DLBCL in the right posterior mandible of a 64-year-old man who was initially misdiagnosed as acute apical abscess and in the right posterior maxilla of an 81-year-old woman who was initially misdiagnosed as chronic periodontitis. These cases demonstrate that it is important for both pathologists and clinicians to consider malignant lesions such as lymphomas in the differential diagnosis of apical radiolucency.

Development of two different histologic types of lymphoma in the same person is rare. Sequential lymphoma is defined as two different types of lymphoma occurring sequentially in the same person. In particular, sequential Hodgkin’s lymphoma (HL) following non-Hodgkin’s lymphoma (NHL) is extremely rare. A 63-year-old female diagnosed with B-cell NHL at the mass in T3 received treatment with an R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone) protocol for six cycles. However, 12 months later, the patient complained of a left neck mass and excisional biopsy was performed. Microscopically the biopsied tissue showed Reed-Stemberg cells and confirmed the diagnosis of HL. The patient was treated with ABVD (adriamycin, bleomycin, vinblastine and dacarbazine) for four cycles. Although the possibility of a secondary malignancy cannot be excluded, this is a rare case of sequential Hodgkin’s lymphoma following Non-Hodgkin’s lymphoma.