CD34 immunostaining of bone marrow biopsy specimens is a reliable way to classify the phases of chronic myeloid leukemia.

Flow cytometry studies have shown that high expression of CD34 antigen in patients with chronic myeloid leukemia (CML) is indicative of accelerated or blastic phases. It has also been suggested that similar information can be obtained by CD34 immunostaining of bone marrow biopsy specimens. To test this hypothesis, the authors studied 59 conventionally fixed, paraffin-embedded bone marrow trephine biopsy specimens, representing the three phases of the disease (stable, accelerated, and blast crisis). Immunohistochemical staining for CD34 was performed using QBEnd10, a monoclonal antibody reactive in routine paraffin-embedded tissue. The differences in CD34 positivity among chronic, accelerated, and blastic phases of CML were highly significant (P = .0001). This study demonstrated that CD34 immunohistochemical staining of bone marrow biopsy specimens represents a reliable method for classifying patients with CML and may provide essential diagnostic and prognostic information when a marrow aspirate is unavailable.