What is the hallmark of all leukemias?

The hallmark of all leukemias is pancytopenia with circulating blasts. This means that in the presence of leukemia, there is a notable reduction in red blood cells, white blood cells, and platelets (pancytopenia), along with the identification of immature white blood cells known as blasts in the peripheral blood. This finding is critical as it signifies the disruption of normal hematopoiesis due to the proliferation of malignant cells, which outcompete and displace normal progenitor cells in the bone marrow.

While the presence of the Philadelphia chromosome is particularly associated with chronic myeloid leukemia (CML) and some acute lymphoblastic leukemias (ALL), it is not a universal feature across all leukemia subtypes. Lymphocytosis can be seen in certain types of leukemia, particularly lymphocytic variants, but it does not apply to all forms, such as myeloid leukemias. Elevated white blood cell counts can be seen in leukemia, but not all leukemias will show this finding, especially in cases where the counts may be low due to extensive bone marrow infiltration and resultant cytopenias. Therefore, the presence of pancytopenia with circulating blasts effectively encompasses the defining characteristics of leukemia as a