Required section · Section 2 of 6
Mental model: three evidence domains
An MPN evaluation joins blood counts, marrow morphology, and molecular findings. Counts describe a pattern, marrow evaluates architecture and lineage morphology, and molecular testing supplies evidence of clonality. The domains answer different questions, so none replaces the others.
Polycythemia vera (PV) often has erythrocytosis with leukocytosis and thrombocytosis because of panmyelosis, meaning increased production in erythroid, granulocytic, and megakaryocytic lineages. Essential thrombocythemia (ET) centers on sustained thrombocytosis and a characteristic megakaryocyte pattern. Primary myelofibrosis (PMF) requires marrow-based assessment and can progress to a leukoerythroblastic blood pattern.
Use either WHO 5th edition or ICC 2022 criteria as named by the report pathway. Do not silently combine their details or turn criteria thresholds into general reference intervals. Identify the evidence domain that remains unaddressed before suggesting the next laboratory step.
Illustrative drawing — this picture was drawn rather than captured.
Reusable integrated evaluation model
Verify the pattern
Confirm persistence, inspect prior counts, and review the smear for artifacts and morphology.
Consider mimics
Assess reactive thrombocytosis and secondary or relative erythrocytosis context.
Integrate studies
Use the named classification framework with marrow and molecular findings.
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