Rapid transformation of atypical chronic lymphocytic leukemia to acute lymphoblastic leukemia.

Transformation of chronic lymphocytic leukemia to acute lymphoblastic leukemia is extremely rare. We describe an elderly patient whose lymphocytes on presentation were morphologically characteristic of chronic lymphocytic leukemia, but changed to lymphoblasts in a very short interval. Peripheral blood mononuclear cells were tested for surface immunoglobulins and T65 antigen at initial presentation as well as at subsequent blastic transformation; on both occasions the majority of cells were devoid of both cell markers. Blast cells in the peripheral blood were positive for terminal deoxynucleotidyl transferase, thus establishing their lymphoid origin (JPMA 37: 269,1987). Most cases of chronic lymphocytic leukemia (CLL) are characterized by circulating surface immunoglobulin positive (slg+) lymphocytes, derived from a single B cell clone. Another antigen, T65, has recently been demonstrated on the surface of nonsecretory CLL cells with the use of TiOl monoclonal antibody. T65 antigen is a T cell specific antigen which is not present on normal B cells but is detected on the surface of nonsecretory, surface immunoglobulin-positive (slg+) cells of CLL patients, thus providing an additional marker for detection of CLL. Transformation of CLL to acute lymphoblastic leukemia (ALL), though extremely rare, has been reported before. However, all the patients who underwent cell marker studies during the chronic and acute phases of the disease, demonstrated slg+ phenotype. T65 antigen was not studied in any of these patients. We describe a unique patient whose lymphocytes, morphologically, were characteristic of CLL on presentation, but lacked slg and T65 antigen (slg-TI 01). Within 4 months acute blastic transformation supervened and shortly thereafter the patient died.