To determine the utility of clinical, morphological and phenotypical features in the differential diagnosis of plasmablastic lymphoma and myeloma with plasmablastic features.

All plasmablastic neoplasms identified from a 15-year retrospective search were reviewed and classified into 'lymphoma', 'myeloma' or 'indeterminate'. The classification was then compared with the previously established clinical diagnosis. Lessons learned from this review were used to design a diagnostic algorithm for pathologists to use in the absence of known clinical history.

The classification was possible in 10 of 11 cases, 8 lymphomas and 2 myelomas (n=2). No distinctive morphological or phenotypical features were identified. The most useful histopathological parameter was a positive Epstein-Barr virus in situ hybridisation. Presence of associated lymphadenopathy and/or oral mass in the absence of complete myeloma-defining signs was used to favour a diagnosis of lymphoma in 4 of 8 cases.

The distinction between plasmablastic lymphoma from plasmablastic myeloma warrants detailed knowledge of clinical, radiological and laboratorial findings. New studies identifying distinctive phenotypical or genetic features are needed to improve the histopathological differentiation of plasmablastic neoplasms.