CD2+ acute promyelocytic leukemia is associated with leukocytosis, variant morphology and poorer prognosis.

The T cell-lineage marker CD2 is sometimes expressed in acute promyelocytic leukemia (APL), and CD2 expression is reported to correlate with some clinical characteristics. However, the significance of CD2 expression in APL has not been fully elucidated. We evaluated CD2 expression in APL treated by the same treatment strategy in a single institute, and whether it had any special characteristics. Among 29 APL, 6 were positive for CD2. Patients with CD2+ APL tended to have a higher leukocyte count than CD2- APL (34.5 +/- 13.1/l vs. 6.8 +/- 2.1/l), morphological characteristics as variant-APL (50 vs. 0%). They also showed poor clinical prognosis. The CR rate of CD2- APL was 87.0% while that of CD2+ APL was 50 %. The mortality was 13.0 and 66.7%, respectively, and the survival rate was significantly lower in CD2+ APL. CD2 expression was proven to be a risk factor associated with death in addition to the morphological characteristics of variant-APL and leukocytosis. These results indicated that CD2 expression might have a significant impact on the prognosis of APL. Whether CD2+ APL should be characterized as a special clinical entity should be discussed in a larger patient population.