ABSTRACT
For BMs done to evaluate myeloproliferative symptoms (usually elevated cell counts on the CBC), CG and molecular testing for В CR/ABL andJAK2 should be done in all cases. The definition of CM L requires the presence of В CR/ABL, and the definitions of the other myeloproliferative neoplasms require its absence. Reactive causes of elevated cell counts are not associated with JAK2. Because JAK2 is positive in virtually all cases of polycythemia vera, this abnormality has become an important element of its diagnosis. Testing for В CR/ABL should be done using FISH since it is cryptic by CG in 10% of cases. JAK2 is identified by PCR. Cytogenetics is also done in these cases to rule out unsuspected abnormalities and because additional defects have prognostic significance for CM L. If there is a substantial eosinophilia, then PDGFRA, PDGFRB and FGFR1 status should ascertained.
