ACUTE MYELOID-LEUKEMIA WITH MINIMAL DIFFERENTIATION - A MULTIPLE PARAMETER STUDY

Acute myeloid leukemia with minimal differentiation (AML-MO) is a rece ntly described entity, and few large studies are available to characte rize its clinical and pathologic features. We reviewed blood and bone marrow morphology, cytochemistry, immunophenotyping and cytogenetics, as well as the clinical findings, of 17 patients with AML-M0. Most pat ients were male, with a median age of 62 years. Minimal background mye lodysplastic features were identified in only 5 of 15 patients. C.ytoc hemical stains for myeloperoxidase and alpha-naphthyl butyrate esteras e were negative in the leukemic blasts of all specimens. Positivity fo r one or both myeloid-associated antigens, CD13 and CD33, was seen in all patients. Both CD34 and HLA-DR were positive in all tested cases. Lymphoid-associated antigens were identified in seven patients; these antigens were typically dim or weak in intensity. Terminal deoxynucleo tidyltransferase positivity was seen in 14 of 14 tested patients; mono clonal anti-myeloperoxidase reactivity was seen in the blasts of 2 pat ients. Abnormal clonal karyotypes were found in 6 of 14 patients. Abno rmalities of chromosomes 7 and 13 were the most common findings, most frequently manifested by monosomy 7 and trisomy 13. The median follow- up was 8 months. Eight patients died of their disease, three are alive with disease, and six are in first or second remission (including thr ee patients treated with bone marrow transplantation). When narrowly d efined, AML-M0 appears to be a homogeneous entity that affects older a nd predominantly male patients, It has no single karyotypic abnormalit y, but complex karyotypes with monosomy 7 and trisomy 13 are commonly found. Acute myeloid leukemia with minimal differentiation is relative ly resistant to chemotherapy; however, bone marrow transplantation may provide a better outcome for eligible patients.