Objective: To report blastic transformation of hairy cell leukemia, an uncommon lymphoproliferative disorder of B-cell lineage.
Design: Routine histology, cytochemistry, and ultrastructural analysis were used to study this case. Immunoperoxidase studies for leukocyte common antigen (CD45), pan B-cell marker L26 (CD20), and hairy cell leukemia marker DBA.44 were performed. In addition, cell surface marker analysis for CD19, CD20, CD5, CD25, CD11c, and kappa and lambda light chains by flow cytometry was performed.
Results: The patient presented with typical clinical, morphologic, cytochemical, immunophenotypic, and ultrastructural features of hairy cell leukemia. Following splenectomy and prior to institution of any other therapy, he developed a blastic lymphoproliferative malignancy with loss of tartrate-resistant acid phosphatase activity, expression of cell surface markers CD11c and CD25, and immunoreactivity for DBA.44.
Conclusion: We believe this to be the first report of such a transformation and recommend that the differential diagnosis of blastic transformation of chronic lymphoproliferative disorders include such a possibility.