Guidelines for using the revised WHO classification of myeloid neoplasms
| Specimen requirements |
| PB and BM specimens collected prior to any definitive therapy. |
| PB and cellular BM aspirate smears and/or touch preparations stained with Wright-Giemsa or similar stain. |
| BM biopsy, at least 1.5 cm in length and at right angles to the cortical bone, is recommended for all cases if feasible. |
| BM specimens for complete cytogenetic analysis and, when indicated, for flow cytometry, with an additional specimen cryopreserved for molecular genetic studies. The latter studies should be performed based on initial karyotypic, clinical, morphologic, and immunophenotypic findings. |
| Assessment of blasts |
| Blast percentage in PB and BM is determined by visual inspection. |
| Myeloblasts, monoblasts, promonocytes, megakaryoblasts (but not dysplastic megakaryocytes) are counted as blasts when summing blast percentage for diagnosis of AML or blast transformation; count abnormal promyelocytes as ″blast equivalents″ in APL. |
| Proerythroblasts are not counted as blasts except in rare instances of ″pure″ acute erythroleukemia. |
| Flow cytometric assessment of CD34+ cells is not recommended as a substitute for visual inspection; not all blasts express CD34, and artifacts introduced by specimen processing may result in erroneous estimates. |
| If the aspirate is poor and/or marrow fibrosis is present, IHC on biopsy sections for CD34 may be informative if blasts are CD34+. |
| Assessment of blast lineage |
| Multiparameter flow cytometry (at least 3 colors) is recommended; panel should be sufficient to determine lineage as well as aberrant antigen profile of neoplastic population. |
| Cytochemistry, such as myeloperoxidase or nonspecific esterase, may be helpful, particularly in AML, NOS, but it is not essential in all cases. |
| IHC on biopsy may be helpful; many antibodies are now available for recognition of myeloid and lymphoid antigens. |
| Assessment of genetic features |
| Complete cytogenetic analysis from BM at initial diagnosis when possible. |
| Additional studies, such as FISH, RT-PCR, mutational status, should be guided by clinical, laboratory, and morphologic information. |
| Mutational studies for mutated NPM1, CEBPA, and FLT3 are recommended in all cytogenetically normal AML; mutated JAK2 should be sought in BCR-ABL1–negative MPN, and mutational analysis for KIT, NRAS, PTNP11, etc, should be performed as clinically indicated. |
| Correlation/reporting of data |
| All data should be assimilated into one report that states the WHO diagnosis. |
| Specimen requirements |
| PB and BM specimens collected prior to any definitive therapy. |
| PB and cellular BM aspirate smears and/or touch preparations stained with Wright-Giemsa or similar stain. |
| BM biopsy, at least 1.5 cm in length and at right angles to the cortical bone, is recommended for all cases if feasible. |
| BM specimens for complete cytogenetic analysis and, when indicated, for flow cytometry, with an additional specimen cryopreserved for molecular genetic studies. The latter studies should be performed based on initial karyotypic, clinical, morphologic, and immunophenotypic findings. |
| Assessment of blasts |
| Blast percentage in PB and BM is determined by visual inspection. |
| Myeloblasts, monoblasts, promonocytes, megakaryoblasts (but not dysplastic megakaryocytes) are counted as blasts when summing blast percentage for diagnosis of AML or blast transformation; count abnormal promyelocytes as ″blast equivalents″ in APL. |
| Proerythroblasts are not counted as blasts except in rare instances of ″pure″ acute erythroleukemia. |
| Flow cytometric assessment of CD34+ cells is not recommended as a substitute for visual inspection; not all blasts express CD34, and artifacts introduced by specimen processing may result in erroneous estimates. |
| If the aspirate is poor and/or marrow fibrosis is present, IHC on biopsy sections for CD34 may be informative if blasts are CD34+. |
| Assessment of blast lineage |
| Multiparameter flow cytometry (at least 3 colors) is recommended; panel should be sufficient to determine lineage as well as aberrant antigen profile of neoplastic population. |
| Cytochemistry, such as myeloperoxidase or nonspecific esterase, may be helpful, particularly in AML, NOS, but it is not essential in all cases. |
| IHC on biopsy may be helpful; many antibodies are now available for recognition of myeloid and lymphoid antigens. |
| Assessment of genetic features |
| Complete cytogenetic analysis from BM at initial diagnosis when possible. |
| Additional studies, such as FISH, RT-PCR, mutational status, should be guided by clinical, laboratory, and morphologic information. |
| Mutational studies for mutated NPM1, CEBPA, and FLT3 are recommended in all cytogenetically normal AML; mutated JAK2 should be sought in BCR-ABL1–negative MPN, and mutational analysis for KIT, NRAS, PTNP11, etc, should be performed as clinically indicated. |
| Correlation/reporting of data |
| All data should be assimilated into one report that states the WHO diagnosis. |
WHO indicates World Health Organization; PB, peripheral blood; BM, bone marrow; IHC, immunohistochemistry; AML, acute myeloid leukemia; APL, acute promyelocytic leukemia; NOS, not otherwise specified; FISH, fluorescence in situ hybridization; RT-PCR, reverse transcriptase–polymerase chain reaction; and MPN, myeloproliferative neoplasm.