In a case of acute leukemia occurring 5.5 yr after diagnosis of Hodgkin's disease, a mixture of lymphoid and myelomonocytoid blasts was identified by morphological, cytochemical, and immunologic methods. The majority of blasts were characterised as lymphoid by their strong expression of nuclear terminal transferase (TdT) enzyme. In contrast, a minor blast population was identified as myelomonocytoid by the strong nonspecific esterase positivity and lack of TdT. The two distinct blast cell populations showed different sensitivity to the various chemotherapeutic protocols used.

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