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13 Plasmablastic myeloma

A 76‐year‐old woman treated with multiple lines of therapy for multiple myeloma presented to clinic with generalised debility and recent heavy nose bleeds. Her paraprotein levels had been noted to be on the rise despite lenalidomide and dexamethasone therapy. The full blood count showed Hb 95 g/l, WBC 3.5 × 10⁹/l, neutrophils 1.5 × 10⁹/l and platelets 18 × 10⁹/l. An IgG paraprotein quantitation was 69 g/l. It was clear that the disease was becoming refractory to therapy but a bone marrow aspirate was taken in view of the problematic thrombocytopenia and bleeding. The aspirate was markedly hypercellular and well over 90% of cells were large pleomorphic plasma cells, some showing prominent nucleoli (images above ×100 objective). Normal haemopoiesis was markedly reduced and megakaryocytes in particular were scarce.

The malignant plasma cells of multiple myeloma are usually easy to recognise allowing accurate quantitation using a manual differential count. The morphology of plasma cells in refractory myeloma, however, often changes with increasing pleomorphism, increasing cell size and multinuclearity. The cells can sometimes resemble those of a high‐grade lymphoma. In addition many of these patients start to shed plasma cells into the peripheral blood (also noted in this case, not shown). Despite their morphological abnormality, the lineage is indicated in this patient by the strongly basophilic cytoplasm and the paler paranuclear Golgi zone. These features are important in helping recognise plasma cells when the nuclear morphology is atypical (images below ×100). Note the variation in nuclear morphology with bilobed and even binucleated forms but the Golgi zone and intense blue cytoplasm are prominent; all of these cells are plasma cells. As an adjunct, note the cytoplasmic fragments and particles due to the intense fragility of plasma cells on handling.

It may be worth reassessing the marrow in patients developing severe cytopenias since, in addition to the above features, some patients sadly develop a treatment‐related myelodysplastic syndrome or acute leukaemia.

MCQ

1 Plasmablastic myeloma:Can represent disease evolutionHas a high proliferation index on Ki‐67 stainingHas a worse prognosis than other cases of myelomaIs associated with worse renal function than other cases of myelomaIs associated with a higher serum calcium than other cases of myelomaFor answers and discussion, see page 206.