Quiz case: Abnormal haematopoietic cells in pleural effusion.

This case was presented because of the number of plasmablasts in a patient with a medical history of multiple myeloma. Flow cytometry is a "gold standard" technique for the diagnosis of haematological malignancies. This technique works for all fluids and should be performed in effusions (pleural, pericardial, ascites) in cases of suspected haematological malignancy. Alternatively, immunohistochemistry using appropriate markers could be performed if flow cytometry is not available. This case illustrates a pleural infiltration by plasmablasts. Myelomatous cells were characterised by immunocytochemistry and flow cytometry.