Introduction
Abnormal monocyte proliferation is a central feature of both juvenile myelomonocytic leukemia (JMML) in children and chronic myelomonocytic leukemia (CMML) in adults. Flow cytometry based monocyte profiling has been found to be a useful aid in the diagnosis of CMML.1-5 Monocytes can be classified into three functionally and immunologically distinct cell populations based on expression of CD14 and CD16 surface markers: classical monocytes (CD14++/CD16-), intermediate monocytes (CD14+/CD16++), and non-classical monocytes (CD14-/CD16++).6-9 Classical monocytes comprise about 90% of the circulating monocytes with only 10% intermediate and non-classical monocytes. 7, 10Absolute count of monocyte subsets by flow cytometry can vary in various disease conditions and provide clinically useful information in management of diseases.7, 11, 12 An increase in the classical monocyte fraction (CD14++/CD16-) greater than 94.0% of total monocytes is considered highly sensitive and specific in distinguishing CMML from other myeloproliferative disorders. 2, 3, 9A specificity of 97% in peripheral blood (PB) and 100% in bone marrow (BM) samples was observed in one study.4
While the distribution and expression of CD14/CD16 surface markers is very well characterized in adult CMML, no such categorization has been reported in JMML. In this pilot study, we evaluated the monocyte partitioning in 14 JMML samples (PB and BM).