Flow cytometry uses a portion of the unfixed liquid aspirate sample. The sample is mixed with a combination of fluorescently-labeled antibodies and the cells are funneled through a flow cell to detect the different fractions via a scattergram. The information provided by flow cytometry is the ratio of specific cell types present.
Hematology smears are made by spreading drops of fresh aspirate specimen on a slide. Touch preps may also be made by gently blotting the biopsy core on slides. The cells are allowed to air dry and then are stained for evaluation. The information provided by hematology is the ratio of cell types present as well as morphology of individual cell types.
Cytogenetics, like flow cytometry and hematology, make use of a portion of the aspirate specimen. The cells are grown in enriched liquid culture medium. After 1-3 days, the cells are induced to undergo mitosis, but then the cells are arrested in metaphase. The cells are dropped onto slides to produce metaphase spreads which are subsequently stained and evaluated for chromosomal abnormalities. The information provided by cytogenetics is chromosomal abnormalities which 1) identify abnormal cells at the nucleic acid level, and 2) help guide treatment.
Histology makes use of the core biopsy primarily, but the leftover aspirate material is also used. The aspirate is allowed to clot in the same way a peripheral blood sample would when collected in the absence of an anti-coagulant. The clotted aspirate and bone marrow core are each placed into formaldehyde and are processed, embedded in paraffin, and sectioned. The information provided by histology is the overall hematopoietic cellularity, fibrosis present, location and quantity of general cell types (red, white, or platelets) in relation to each other. Also, monomorphic cell populations can often be identified by histology.
Rarely does a pathologist rely on one method alone of bone marrow testing. It is important to assimilate the information provided by all four areas of the lab to provide the best diagnosis for the most successful treatment of the patient.
To learn more, register for the 2021 NSH Convention and attend Dr. Criswell's workshop, WS-12 Evaluation of Bone Marrow Biopsies with Hematology, Histology, Flow Cytometry, and Cytogenetics, Tuesday, Sep 14; 4:15 PM ET - 5:15 PM ET.
Written by Shelia Criswell, PhD, HTL(ASCP)QIHC