Plasmablastic neoplasms with unusual histomorphology: A report of two cases

Plasmablastic neoplasms comprise a heterogeneous group of haematolymphoid neoplasms which includes plasmablastic lymphoma (PBL), and plasmablastic plasma cell myeloma. Distinguishing the two entities remains a major diagnostic challenge. We herein report on two HIV-positive patients with plasmablastic neoplasm displaying unusual morphology, including multinucleated giant cells, crystalloids and a foreign body type giant cell reaction. The two cases both showed proliferation of plasmablasts, immunoblasts and centroblasts with expression of MUM1, VS38c, EBER positivity, light chain restriction and high proliferative indices. The case showing crystalloids, in addition showed abnormal bone marrow monoclonal plasma cells and positive multiple myeloma cytogenetic studies, and was concluded as plasmablastic plasma cell myeloma. The other case with anaplastic and multinucleated giant cells showed normal bone marrow haematopoiesis and was diagnosed as a plasmablastic lymphoma. These two cases highlight the unusual morphological presentation of PBL and PPM whilst illustrating diagnostic challenges in differentiating the two entities.