Human immunodeficiency virus (HIV) is a serious worldwide healthcare problem with implications for all healthcare workers. The reported oral manifestations of the disease are numerous and have been categorised according to the strength of their association with HIV infection. Oral non-Hodgkin's lymphoma is strongly associated with HIV infection, and an increased incidence of such neoplasms is widely reported. This case report details the presentation of a rare subcategory of plasmablastic lymphoma in an HIV-positive patient after administration of an inferior alveolar dental block to facilitate extraction of mandibular teeth. This highly aggressive neoplasm is a large B-cell lymphoma with a predilection for the oral cavity. Unfortunately, the prognosis for such a tumour is poor as detailed in this case.