Plasmablastic lymphoma may manifest in extra-oral locations such as the orbit, most commonly in patients with a history of AIDS. On imaging, PBL appears as a soft tissue mass differentiated from several other etiologies by avid FDG uptake on PET/CT scanning and is definitively diagnosed by characteristic histological markers on pathological examination.

From the manuscript

Orbital plasmablastic lymphoma with remission following chemotherapy

Abstract
We report the case of a middle-aged HIV-positive man who presented with proptosis and retro-ocular pain. On CT and MR imaging, a retro-orbital enhancing mass was seen, and PET/CT revealed this lesion as well as a similarly characterized mass in the nasopharynx to be hypermetabolic. Biopsy and subsequent pathological characterization revealed this mass to be plasmablastic lymphoma (PBL), a rare form of non-Hodgkin`s lymphoma associated with HIV-infection. PBL is a diffuse B-cell lymphoma with characteristic cell marker patterns. The most common site of this malignancy is within the oral cavity. This case constitutes an unusual orbital manifestation of plasmablastic lymphoma as well as an unusual case in its response to chemotherapy. This case illustrates the importance of functional imaging with PET/CT in the diagnosis, management, and follow-up of plasmablastic lymphoma.