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).