The value of immunohistochemistry for CD14, CD123, CD33, myeloperoxidase and CD68R in the diagnosis of acute and chronic myelomonocytic leukaemias.

AIMS

In the absence of adequate aspirate films and touch imprints, distinction of chronic myelomonocytic leukaemia (CMML) from acute myeloid leukaemia with monocytic differentiation (Mo-AML) may be difficult solely on the basis of bone marrow biopsy morphological features. The aim of this study was to evaluate the diagnostic utility of a novel immunohistochemical panel for the diagnosis of acute and chronic myelomonocytic leukaemias in bone marrow biopsies.

METHODS AND RESULTS

Immunohistochemical labelling for CD14, CD123, CD33, myeloperoxidase (MPO) and CD68R was assessed in 49 myeloid neoplasms with monocytic differentiation (24 CMMLs and 25 Mo-AMLs) and compared with that of 15 non-monocytic acute myeloid leukaemias (NM-AMLs) and 17 non-neoplastic controls. More than 20% CD14 immunohistochemistry (IHC)+ cells were seen only in Mo-AMLs and CMMLs, although Mo-AMLs showed wide variability and overlapped with other categories. More than 20% CD68R IHC+ cells had the highest sensitivity and specificity for Mo-AML. Discrepant MPO-/CD33+ expression was specific for Mo-AML but insensitive. A subset of blasts in Mo-AMLs and NM-AMLs were weakly CD123+.

CONCLUSIONS

A significantly increased number of CD14+ cells raises the possibility of a myelomonocytic neoplasm but does not distinguish between CMML and Mo-AML. Significantly increased numbers of CD68R IHC+ cells and a discrepant MPO-/CD33+ staining pattern are specific for Mo-AML but are best utilized in a comprehensive panel.