Acute myeloblastic leukemia with minimal myeloid differentiation: phenotypical and ultrastructural characteristics

Abstract

AML-M0 is an infrequent form of acute myeloblastic leukemia characterized by negative reaction with myeloperoxidase (MPO), Sudan Black and lymphoid antigens and positivity for CD13 or CD33. In the present study we describe the immunophenotypical and ultrastructural characteristics of a group of AML-M0 in adult patients. Nine out 218 AML leukemias (4.1%) fulfilled the AML-M0 criteria. CD13 or CD33 were positive in eight out nine cases, with two or more positive myeloid antigens being present in 82% of the cases. Immunological MPO was positive in 57% of the cases and CD68 in 33%. In no case were megakaryocytic and erythroid markers present. Four cases (44%) expressed CD7 and TdT but only two coexpressed both antigens. In none of the cases was CD3 or CD22 cytoplasmic expression found. Ultrastructurally, a low number of granules was seen in all cases whereas ferritin particles or rhopheocytosis were not observed. Ultrastructural MPO was positive in one out of five cases and platelet peroxidase (PPO) was negative in the four cases studied. Two out of six cases showed karyotypic abnormalities (hypotetraploidy and a complex karyotype, respectively). In two out three cases a rearranged pattern for J H gene was observed. TCR (C␤ and J␥) rearrangements were not detected in any case. AML-M0 is an infrequent form of acute myeloblastic leukemia. A large panel of myeloid monoclonal antibodies (MoAb) and the study of the cytoplasmic expression of myeloid antigens is necessary to diagnose this form of leukemia. AML-M0 usually coexpress lymphoid markers. Ultrastructural studies may be of help to discard an immature erythroid proliferation.

Low expression of the myeloid differentiation antigen CD65s, a feature of poorly differentiated AML in older adults: study of 711 patients enrolled in ECOG trials

“…35 Conversely, AML with FAB-type M0, the subtype with the least morphologic differentiation, 12 develops preferentially in older patients (Z60 years of age). [36][37][38][39][40][41][42] Historically, but even in the recent WHO classification, 43 immunophenotypically minimally differentiated AML has been considered synonymous with FAB M0. Recent reviews of laboratory findings and proposals for new diagnostic criteria of minimally differentiated AML have focused on better defining AML-M0.…”

True

“…27 The positivity of leukemic cells for CD34, a marker of hematopoietic stem cells, is common in AML-M0, M1 or M7, and rarely seen in AML-M2 to M5. 8,28,29 The high percentage of CD34 + leukemic precursors in the AML-M0 leukemia model allowed us to test their differential immune recognition in comparison with more differentiated blasts.…”

Rare coincidence of hypertriploid chromosome number and aberrant coexpression of the lymphoid-associated antigen CD5 in acute myeloid Leukaemia FAB M0

“…5 Some authors reported that AML M0 is significantly associated with the coexpression of lymphoidassociated markers (ie CD4 or CD7). 6,7 The incidence of CD5-positive AML is 3% in children and 4% in adults and is distributed similarly through all FAB types. 5,7 The coexpression of lymphoidassociated markers does not seem to be associated with an adverse overall survival in these patients.…”