High-Grade B-Cell Lymphoma Not Otherwise Specified (HGBL, NOS) in the Maxillary Sinus Mimicking Periapical Inflammation: Case Report and Review of the Literature

High-grade B-cell lymphoma not otherwise specified is listed as a new group in the WHO 2017 statement as a subtype of aggressive, mature B-cell lymphomas with a poor prognosis. To our knowledge, no description of this genetic type of maxillary lymphoma has appeared in the literature until now; thus, our case provides valuable data on its symptoms, clinical behavior, response to treatment and survival rate. The present report describes the early diagnosis and treatment of an extremely rare histological subtype of B-cell lymphoma, a case of high-grade B-cell lymphoma not otherwise specified, localized in the maxillary sinus and mimicking signs and symptoms of periapical inflammation. After chemotherapy, the presented patient showed complete remission without relapse and systemic spread. As far as we know, this is the first reported case of this rare type of lymphoma associated with the maxillary sinus. Considering that high-grade B-cell lymphomas are aggressive tumors with rapid growth and poor prognosis, which are often misdiagnosed in the early stages as inflammatory disease, it is relevant to highlight the importance of a detailed evaluation of clinical signs and radiological findings during diagnosis, especially if they contradict each other.