Significance of Phi bodies in acute leukaemia.

Material from 39 patients with acute leukaemia was investigated with the peroxidase cytochemical reaction using 3,3'diaminobenzidine (DAB) and other substrates in order to test their sensitivity in detecting myeloid differentiation. The proportion of positive blasts and of cases with Auer rods in acute myeloid leukaemia (AML) was significantly greater with DAB than with benzidine. In addition, Phi bodies were demonstrated in AML blasts only when DAB was used; Phi bodies were also observed in two out of seven cases of chronic granulocytic leukaemia in "myeloid" blast crisis but were not seen in any case of acute lymphoblastic leukaemia.