Plasmablastoma lymphoma (PBL) is a highly aggressive form of large B-cell lymphoma in which the neoplastic cells resemble B immunoblasts and have a plasma cell immunophenotype. PBL is most common in HIV-positive male patients, but may also be seen in other immunocompromised patients. Cases have also been described in those without immunodeficiency, but these tend to arise in the elderly.

EBV co-infection is present in the majority of PBL. A relationship with HHV8 is questionable. The most common site is he oral cavity, but other mucosal sites may also be involved including sinonasal cavity, orbit, skin, bone, soft tissues and GI tract. Lymph nodes are rarely involved (Swerdlow).

Histologically, PBLs are composed of monotonous large cells with eccentrically located vesicular nuclei, amphophilic cytoplasm and a paranuclear hof (Fletcher).

The neoplastic cells are positive for plasma cell markers with weak or no expression of B-cell markers. Thus, the cells are positive for CD138, CD38 and MUM1 and are negative for CD45, CD20 and PAX5. In terms of cytogenetics, there is clonal IgH gene rearrangement.