Minimally differentiated acute myeloid leukemia in Taiwan: predominantly occurs in children less than 3 years and adults between 51 and 70 years

Abstract

Acute myeloid leukemia (AML) with minimal differentiation was usually referred to as acute undifferentiated leukemia in the past. With the help of immunophenotyping, this subtype of leukemia was shown to express myeloid antigens on the blasts and was designated AML-M0 by FAB Cooperative Study Group in 1991. Among the 423 consecutive newly diagnosed de novo AML at our institution, 12 (2.8%) were of M0 subtype. The proportion of M0 in AML was higher in children than in adults (8.2% vs 1.7%). Four other M0 patients referred from outside hospitals for immunophenotyping were also included in this study. There were two peaks in age distribution of these 16 patients: less than 3 years and between 51 and 70 years, respectively. Organomegaly was more common in patients with AML-M0 than in those with other subtypes (56.3% vs 29.2%, P = 0.025). The former patients had higher incidences of CD7 and CD34 expression on the leukemic cells than the latter ones (50% vs 16.9%, P = 0.003 and 69.2% vs 37.9%, P = 0.019, respectively). The patients with AML-M0 showed more frequent clonal chromosomal abnormalities in the leukemic cells than other AML patients (83.3% vs 53.9%, P = 0.039); the same is also true for complex cytogenetic aberrations (50% vs 11.4%, P = 0.004). Adults with AML-M0 showed a lower complete remission (CR) rate and significantly poorer survival than those with non M0-AML. However there was no significant difference in outcome between the two groups of pediatric patients. In conclusion, AML-M0 is a unique subtype of leukemia that has distinct age distribution and shows different clinical and biological characteristics from other AML. Adult patients have poor prognosis. Whether pediatric patients had better outcome than adults needs to be clarified in further studies.

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

“…36,37,41,52 However, while it is obvious that AML-M0 occurs predominantly in older adults, as discussed before, response rate and response duration across the board have been compared to AML patients of all ages, and statistical analyses have not been adjusted for this established significant prognostic covariate. To the point, in a series of M0 cases reported from Taiwan, 38 only the adult patients (median age of 57 years) showed poorer outcome when compared to non-M0 AML; the pediatric M0 cohort did not demonstrate a significant difference in clinical response when compared to an age-adjusted control group. This observation suggests that the inferior outcome of morphologically poorly differentiated AML may be the result of older age.…”

“…It would be tempting to suggest that CD65s could be that antigen, the lack of which characterizing AML M0. Although several clinicobiological features attributed to AML M0 were not observed in CD65s low AML, such as a higher incidence of unfavorable cytogenetics when compared to more mature AML, excessive expression of P-glycoprotein, or a high frequency of lymphoid-affiliated antigens, 38,39,41,44,46,47 there is strong evidence in favor of CD65s as a hallmark of myeloblast maturation.…”

“…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.…”

Minimally differentiated acute myeloid leukemia (FAB AML-M0) is associated with an adverse outcome in children: a report from the Children's Oncology Group, studies CCG-2891 and CCG-2961

“…[1][2][3][4][5][6][7][8] Since its recognition as a distinct entity in 1987, 9 the French-AmericanBritish (FAB) Cooperative Group has proposed that the criteria for a diagnosis of AML-M0 consist of the presence of less than 3% myeloperoxidase (MPO)-and/or sudan black B (SBB)-positive blasts in the bone marrow (BM) by light microscopy, myeloidassociated antigen positivity (CD13 and/or CD33), and lack of B-/T-cell lineage-associated antigen expression, with the exception of TdT, CD7, and CD4. 10 Despite the formulation of this generally accepted definition, the unequivocal recognition of this AML subtype continues to pose certain challenges, with many investigators shaping the FAB guidelines into varying institutional definitions.…”

“…11 To date, the presenting characteristics and the outcome of patients with AML-M0 have primarily been described in small cohorts of adult patients, where the consistent feature has been a low remission induction rate and a short remission duration. [1][2][3][5][6][7][8] Little is known regarding the clinical and biologic significance of the FAB AML-M0 subtype in children. 5,7,11 Three identified studies reporting children with AML-M0 are limited by small sample size, 5,7 the administration of heterogeneous therapies, 11 and a lack of adequate follow-up.…”