Normoblasts in pleural fluid: are they significant?

The hemopoietic cell elements in body fluids is a rare encounterance. From among the normal bone marrow inhabitants, only megakaryocytes are occasionally seen in pleural and peritoneal fluids due to extramedullary hemopoiesis as a result of myeloproliferative disorders. The finding of isolated normoblasts in body fluids with no other marrow elements is described here for the first time in pleural fluid from two patients. The normoblasts which have a close resemblance morphologically to mesothelial cells, need to be differentiated from one another. A supravital stain is of help when in doubt. Because of their close resemblance, normoblasts may get missed during evaluation. This report highlights the need for a larger number of positive cases with emphasis on their course details to understand the significance of normoblasts in body fluids. Diagn. Cytopathol. 2007;35:590-592. © 2007 Wiley-Liss, Inc.