Proposal for a classification of acute myeloid leukaemia based on plastic-embedded bone marrow biopsy sections

Traditional approaches to haematological diagnosis of acute myeloid leukaemia (AML) include microscopic examination of peripheral blood (PB) and bone marrow (BM) cells studied in Romanowsky-stained, dry film smears. The routine evaluation of BM aspirates, however, may be disappointing in accurately assessing marrow activity because of the sampling error inherent in the BM aspiration technique, and occasionally may fail to provide a precise diagnosis because BM aspirates cannot be obtained due to packed or fibrotic marrows. Because of the advantages it offers over the conventional method of diagnosis, we have studied Romanowsky-stained, thin sections of plastic-embedded BM biopsies from 87 newly diagnosed AML patients. Based on our study, the patients were broadly grouped into four categories: (1) those with hypocellular marrow (haemopoietic cellularity less than 50%), hypoplastic AML; (2) those with some degree of marrow fibrosis, AML with marrow fibrosis; (3) those with homogeneous infiltration of marrow with blast cells; and (4) those with inhomogenous infiltration of marrow with blast cells. Our results show that the proposed classification of AML based on the evaluation of plastic-embedded BM biopsy sections may offer benefits over those afforded by conventional morphologic smear techniques. This may provide significant prognostic information and may have a major impact on patient management. It may also provide a meaningful stratification of the patient population when comparing treatment protocols for newly diagnosed AML patients.