Chromosome change at 16q22 in nonlymphocytic leukemia: clinical implication on leukemia patients with inv(16) versus del(16).

Nineteen patients with inv(16)(p13q22) or del(16) in myeloid leukemia are described. Eight showed inv(16)(p13q22), including one with de novo acute myeloid leukemia (AML-M2) and seven with de novo acute myelomonocytic leukemia (AMML-M4). Additional chromosome changes were detected in five of the cases; the most common change was trisomy 22. All but one of the de novo M2 and M4 leukemia patients with inv(16)(p13q22) showed initial bone marrow eosinophilia (greater than 5%) with basophilic granules. The remaining 11 showed deletion of the long arm of a chromosome no. 16 [del(16)(q22 or q23)]. Eight of the 11 were diagnosed as having chronic myelomonocytic leukemia, three transformed into an acute phase with M4 morphology; none of them gained complete remission. Two of the remaining three patients with del(16) were diagnosed as having M4 leukemia without marrow eosinophilia. The remaining one was a case of M4 leukemia following a myelodysplastic syndrome. The findings indicate that del(16) might be related to chronic myelomonocytic leukemia or leukemia with a prior history of myelodysplastic syndrome without evidence of marrow eosinophilia. On the other hand, inv(16)(p13q22) is highly associated with de novo AML especially AMML-M4 with bone marrow eosinophilia and a favorable prognosis.