Cytoplasmic fragments causing spurious platelet counts in hairy cell leukemia: ultrastructural characterization

A patient with hairy cell leukemia had a spuriously elevated automated platelet count because of cytoplasmic fragments. The cytoplasmic fragments observed with electron microscopy were found in the same fraction as the platelets (platelet-rich plasma). Ultrastructural examination confirmed the hairy cell cytoplasmic origin of these fragments because of their obvious difference from platelet ultrastructure. Cytoplasmic fragments as a cause of spuriously high automated platelet counts should be considered in all cases of hairy cell leukemia. The blood smear can suggest these factitious events and should be used to confirm the platelet count. It is important to validate the automated platelet count even when reported values are within the normal range, since electronic counting may result in a spurious thrombocytosis or a spuriously normal count.