Chronic Lymphocytic Leukemia with Prolymphocytic Transformation Simulating Hairy Cell Leukemia

We report a case of chronic lymphocytic leukemia in prolymphocytic transformation. Although the clinical findings in this patient were similar to those of some cases of hairy cell leukemia, many of the leukemic cells were morphologically typical of prolymphocytes. Cytochemical staining for tartrateresistant acid phosphatase (T-AcP) and immunochemical analysis of mononuclear cells revealed a phenotype very much like that of hairy cells. Aside from morphologic differences from hairy cells, the only other distinguishing feature of these prolymphocytes was a focal T-AcP staining pattern unlike the diffuse pattern seen in hairy cells. This case illustrates how diagnostic difficulties may arise if too much emphasis is placed on immunochemical and cytochemical results without serious consideration of morphologic details. (The J Histotechnol 10: 127,1987)