Bone Marrow Differential Count: Workflow and Cell Classification

Purpose and specimen quality

The aspirate permits detailed cytological assessment, while the trephine biopsy contributes architectural information; they are complementary. Current ICSH guidance calls for systematic examination with low-power review of particles and trails followed by high-power cytological assessment. It places the nucleated differential in well-preserved trails adjacent to representative particles and states that markedly hemodilute or aparticulate samples are unsuitable for a reliable count. [1]

The founder describes concern when an aspirate is aparticulate or has very poor representative marrow particles or trails and its cellular composition resembles peripheral blood. He assesses the whole preparation rather than relying on the absence of a single cell type. This is a practical observation, not a standalone universal adequacy threshold.

Count and classify in context

The current ICSH guidance describes granulocytic, monocytic, and erythroid precursors, lymphocytes, plasma cells, and mast cells within the nucleated differential; megakaryocytes and stromal or other non-hematopoietic cells are assessed but excluded from that denominator. [1]

1. Confirm aspirate identity, adequacy, and the local denominator and category rules.
2. Choose representative, well-preserved cells in appropriate particle trails.
3. Progress through fields consistently; classify eligible nucleated hematopoietic cells by lineage and maturation.
4. Record blasts and other clinically important populations according to the laboratory’s rules and seek review of uncertain cells.
5. Reconcile the actual total and category counts before calculating proportions.
6. Document adequacy, total assessed, lineage findings, abnormal populations, and limitations for the integrated report.

Practical points that may need a second look

From the founder’s practice, two important workflow problems are entering the wrong cell category in a counter or phone app and difficulty classifying challenging morphology, including immature or atypical cells. These are first-hand observations, not measured error rates or prevalence estimates. Check entries against the observed cells and use the laboratory’s review pathway when cell identity is uncertain.

Interpretation and limitations

The aspirate report should summarize specimen adequacy, lineage assessment, abnormal populations, and a morphology-based interpretation, then be integrated with relevant investigations. An isolated percentage should not be treated as a diagnosis. [1]

Focal aggregates, hemodilution, poor preservation, and uncertain cell identity can all affect what a tally represents. The reviewer decides whether another preparation, a second observer, or an additional modality is needed under the applicable protocol.

The founder reports generally following accepted hematology, ICSH, and WHO principles alongside local laboratory practice rather than applying a separate one-size-fits-all count rule. Near a potentially important classification threshold, his approach is to consider morphology, specimen adequacy, a count appropriate to the question, applicable classification criteria, and a second review when needed rather than rely on one borderline percentage. This is an attributed practice example, not a numeric or universal rule.

In his practice, suspected leukemia, a suspected myelodysplastic neoplasm (MDS), unusual immature cells, or other classification uncertainty may prompt a second opinion. Additional cells, another smear, or another preparation may also be considered when the initial material is inadequate, hemodilute, aparticulate, or not representative. This does not mean every leukemia or MDS case requires the same count or review sequence.

Using HemaSync for a marrow tally

HemaSync can hold the observer’s manual category entries and count target. It does not identify marrow cells, assess adequacy, calculate an integrated diagnosis, or replace a pathologist or trained laboratory professional. Any AI-assisted text is supportive and requires professional interpretation.