Hematopathology

Overview
Hematopathology is the branch of pathology which studies diseases of hematopoietic cells (see below). A hematopathologist looks at peripheral blood smears, bone marrow aspirates and biopsies, lymph nodes, and other tissues, and uses his/her expertise to diagnose diseases such as lymphomas and leukemias. The hematopathologist uses traditional microscopy to look at the specimen, but also relies on laboratory values, immunohistochemistry, flow cytometry, and molecular diagnostic tests to make the most accurate diagnosis. The hematopathologist works closely with the hematologist/oncologist specialty doctor who sees the patient and decides on the best treatment based upon the diagnosis.

Diseases of Hematopoietic Cells
The major disease of hematopoietic cells fall into several categories, which include chronic myeloproliferative disease, myelodysplastic syndromes, leukemias, lymphomas, plasma cell neoplasms, and histiocytic and mast cell neoplasms. Hematopathologists from all over the world have agreed on a standard classification system, called the "WHO classification". Leukemias are mainly bone marrow and blood based and can be subclassified as chronic leukemia and acute leukemia. Chronic leukemia is the proliferation of too many mature blood cells, and is called that because it is a chronic process clinically. Examples are chronic myelogenous leukemia and chronic lymphocytic leukemia. Acute leukemia is the proliferation of too many immature blood cells, called myeloblasts, which have lost the ability to become mature cells. This is usually a very aggressive disease if untreated. Fortunately, treatment of both types of leukemia has improved greatly over the past few decades. Lymphomas are diseases that are mainly based in lymph nodes. Hematopathologists have named different lymphomas after the type of lymphocyte that has become malignant. Thus there are B cell lymphomas, T cell lymphomas, and NK cell lymphomas. The hematopathologist uses immunohistochemistry and flow cytometry, techniques using antibodies to specific lymphocyte surface markers, to determine the type of lymphoma in the pathology specimen.