Basophilia

Excerpt

Basophils are typically the least numerous myeloid cells seen in a peripheral blood smear. Their numerous dark azurophilic granules easily distinguish them. Basophilia is not a common finding in peripheral blood. Most commonly, it is a reactive mechanism often seen in combination with eosinophilia and an absolute basophil count of greater than 200 cells/uL. Different ranges are set depending on the laboratory and also based on the local population. If performed, bone marrow aspirates may show an increase in basophils or precursors.

Basophils express CD45 and are positive for myeloid markers CD13, CD11b, and CD33. They also express CD22 (also positive in B-cells), bright CD38, and bright CD123.