Relative contributions of enzyme cytochemistry and flow cytometric immunophenotyping to the evaluation of acute myeloid leukemias with a monocytic component and of flow cytometric immunophenotyping to the evaluation of absolute monocytoses

We evaluated the contributions of enzyme cytochemical stains and flow cytometric immunophenotyping (FCI) data to detection of monocytic cells (MCs) in acute myelomonocytic and acute monocytic leukemias (AMMLs and AMoLs) and compared FCI findings in AMoL, chronic myelomonocytic leukemia (CMML), and normal peripheral blood (PB) and bone marrow (BM) monocytes to classify and evaluate absolute monocytoses (AMs). We reviewed 10 AMMLs and 6 AMoLs with alpha-naphthyl-acetate esterase (ANAE) and alpha-naphthyl-butyrate esterase stains and a complete FCI profile and compared FCI data for 6 AMoLs, 7 CMMLs, 2 AMs, and normal monocytes. We confirmed increased sensitivity of ANAE staining to FCI data in detecting MCs in AMML and AMoL. CD14 was insensitive for confirming MCs; other characteristic markers of MCs were absent or partially lost in AMML and AMoL. Aberrant expression of CD56 (detected in 50% of AMMLs and AMoLs), CD34, and CD117 indicated malignancy. The mature MCs of the CMMLs revealed variable FCI abnormalities (partial loss of CD13, CD14, and CD15; expression of CD56), as in the monoblasts of AMoL. These FCI abnormalities in morphologically mature MCs might indicate markers for CMML. AMs revealed FCI abnormalities, indicating clues to their correct classification as CMML.