in normal individuals, BM B-cell precursors varied mainly according to age, but were also dependent on technical peculiarities of operators and equipments. Analysis by phenotype and as percentage of total nucleated cells was more accurate and less susceptible to variation than evaluating % BCPs/total CD34 cells. © 2017 International Clinical Cytometry Society.

Phenotypic abnormalities were similar to those found in adult MDS. A decrease in B-cell precursors was observed especially in RAEB/RAEB-t. JMML and RAEB showed a similar pattern.

The diagnosis of juvenile myelomonocytic leukaemia (JMML) is based on clinical, laboratory and molecular features but immunophenotyping [multiparametric flow cytometry (MFC)] has not been used routinely. In the present study, we describe the flow cytometric features at diagnosis with special attention to the distribution of monocytic subsets and the relation between MFC and molecular subgroups. MFC was performed with an eight-colour platform based on Euroflow. We studied 33 JMML cases. CD34 + /CD117 + /CD13 + cells >2% was found in 25 cases, and 51Á5% presented an aberrant expression of CD7. A decrease of CD34 + /CD19 + /CD10 + cells was seen in eight cases and in four they were absent. The granulocytic population had a decreased side scatter in 29 cases. Bone marrow monocytic precursors were increased in 28 patients, with a decrease in classical monocytes (median 80Á7%) and increase in CD16 + (intermediate and nonclassical). A more pronounced increase in myeloid CD34 + cells was seen in patients with Neurofibromatosis type 1 (NF1) and tyrosine-protein phosphatase non-receptor type 11 (PTPN11), with aberrant CD7 expression in four of six and 10/12 patients respectively. Thus, JMML shows an immunophenotypic profile similar to myelodysplastic syndromes, and a different monocyte subset distribution when compared with chronic MML. MFC proved to be an important diagnostic tool that can help in differential diagnosis with other clonal diseases with monocytosis.

Juvenile myelomonocytic leukaemia (JMML) is a rare clonal haematopoietic neoplasm from early childhood with characteristics of both myelodysplastic and myeloproliferative syndromes. It represents 3% of all haematologic malignancies in paediatric patients. [1][2][3] Most patients present mutation of genes of the Rat Sarcoma (RAS) pathway such as the genes tyrosine-protein phosphatase non-receptor type 11 (PTPN11), KRAS proto-oncogene, GTPase (KRAS), NRAS proto-oncogene, GTPase (NRAS), Casitas B-lineage lymphoma (CBL) and neurofibromin 1 (NF1). [4][5][6][7][8]