Plasmablastic Lymphoma and Multicentric Castlemans Disease

This is a great blood film - assuming it's not yours, that is. This patient is HIV positive with a history of an immune dysregulation syndrome called Castlemans disease. What they actually have is a combination of plasmablastic lymphoma, and Castlemans disease. This patient had multicentric Castlemans with a massively elevated IL-8. He was actually KSHV negative (KSHV/HHV8 is associated with MCD). You should be able to get plasmablastic lymphoma by morphology but the Castlemans is a bit niche. 

The blood film is full of abnormal cells. There are immature lymphoid cells - morphologically they are blasts but the flow suggested they were lymphomatous, so expressing some markers of maturation. There are abnormal monocytes, which are extremely reactive and could be consistent with either diagnosis. There are immature plasma cells - plasmablasts - with deep dark cytoplasm laden with abnormal Immunoglobulins and which again feed the immune dysregulation. As part of the bone marrow infiltration, there are nucleated red blood cells. Surprisingly, the myeloid series is relatively normal. There are neutrophils, which are reactive. There is a significant thrombocytopenia with platelet anisocytosis. Whether this is bone marrow failure or an associated immune ITP-like destruction we never found out. The red cell morphology is surprisingly pretty normal, apart from an anaemia. There is some mild RCAP, and a few acanthocytes and reticulocytes but this does not look at all like a primary bone marrow / red cell disorder.

Overall, the extreme reactive change and plasmablasts should be making you think plasmablastic lymphoma. It couldn't really be plasma cell leukaemia - plasma cells are by definition mature cells, and these by morphology and flow are highly immature. It could be another form of unusual leukaemia - but if you've covered LPD and described plasma-cell type features, then you've got off to a great start.