MINIMALLY DIFFERENTIATED ACUTE MYELOID-LEUKEMIA (AML-MO) - CYTOCHEMICAL, IMMUNOPHENOTYPIC AND CYTOGENETIC ANALYSIS OF 19 CASES

We describe our experience in the identification of 19 cases of AML-MO categorized among 200 consecutive AML cases. Leukaemic cells from our cases were morphologically marked by agranular basophilic cytoplasm, finely dispersed chromatin and prominent nucleoli. In two cases heavil y vacuolated and monocytoid-shaped blasts were also observed. Cytochem istry (MPO, SBB, alpha ANAE, alpha NBE, NASDCAE, AP, PAS) was negative in 14 cases, five cases expressing a very faint cytoplasmic positivit y for alpha NBE (not exceeding 30% of the blasts) and alpha ANAE (not exceeding 41%) which was sodium fluoride resistant. In these five case s other monocytic markers (e.g. CD14) were not in favour of myelomonoc ytic differentiation. All the cases were anti-MPO positive at frequenc y >10%. Phenotypic analysis also revealed myeloid features with all th e patients having at least one myeloid antigen (CD13, CD33, CD15), Tdt was expressed in nine cases and CD7 in six cases. All cases but one w ere positive for CD34. Cytogenetic analysis, performed in 16 cases, sh owed no adequate growth in two cases and no consistent abnormality in four; among the remaining 10 cases no consistent abnormality was obser ved, the most common finding was trisomy 8 (two cases) and 4 (two case s) and aberrations of chromosomes 2, 3, 5, 7, 9, 12 and 21. No cases o f (t9;22), Ph chromosome were observed. Interestingly three out of fiv e patients with faint alpha NBE/alpha ANAE positivity relapsed as typi cal M4 (one case) or M5a (two cases).