Hematopathology and Transfusion-Related Morphology
Hematology morphology
Start with the CBC: anemia is classified by mean corpuscular volume. Microcytic: iron deficiency, thalassemia, anemia of chronic disease, sideroblastic anemia. Normocytic: acute blood loss, hemolysis, renal disease, marrow failure. Macrocytic: B12/folate deficiency, alcohol, myelodysplasia. The peripheral smear adds shape (schistocytes, spherocytes, target cells, sickle cells) and inclusions (Howell–Jolly bodies, basophilic stippling, Auer rods). Reticulocyte count separates decreased production from increased loss.
Bone marrow: acute leukemias show blasts; Auer rods indicate acute myeloid leukemia, particularly promyelocytic leukemia with t(15;17). Chronic myeloid leukemia shows the Philadelphia chromosome and BCR-ABL1. Myeloproliferative neoplasms include polycythemia vera, essential thrombocythemia, and primary myelofibrosis, with JAK2 mutations. Lymphoma: Hodgkin lymphoma has Reed–Sternberg cells in an inflammatory background; non-Hodgkin lymphoma includes follicular, diffuse large B-cell, Burkitt (starry sky), and mantle cell. Flow cytometry immunophenotypes.
Transfusion
Blood products: packed red cells, platelets, fresh frozen plasma, cryoprecipitate. Reactions: acute hemolytic (ABO incompatibility), febrile non-hemolytic, allergic, TRALI, TACO, delayed hemolytic. Type and screen, crossmatch, and the direct antiglobulin test are core.
Traps
Questions swap acute and chronic leukemia, or confuse TRALI with TACO. Auer rods are never in lymphoid leukemia.
Rule of thumb: high RDW with low ferritin suggests iron deficiency; normal RDW with target cells suggests thalassemia trait.
Worked example: microcytic anemia, low ferritin, high RDW - iron deficiency; treat and recheck.