Chloroacetate esterase positivity in acute lymphoblastic leukemia

Chloroacetate esterase (CAE) reactivity is associated with acute nonlymphocytic leukemia (ANLL) and, to the author's knowledge, has not been reported in acute lymphoblastic leukemia (ALL). The authors have identified a single patient whose blasts displayed CAE reactivity from a review of 400 newly diagnosed patients with ALL. The diagnosis of ALL in this case was based upon morphologic evaluation (FAB:L1), presence of terminal deoxynucleotidyl transferase (TdT), the absence of reactivity with myeloperoxidase, and the failure of leukemic blasts to mark with a panel of anti-myeloid monoclonal antibodies. Remission was induced promptly with standard ALL therapy. This case demonstrates that punctate CAE positivity rarely can occur in ALL, and, therefore, CAE is not entirely specific for ANLL. The authors conclude that CAE positivity should not be used as a sole criterion to diagnose ANLL in the absence of supporting morphologic, cytochemical, immunocytologic, or clinical information.