Hematopathology is the branch of pathology

Pathology

Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....

 which studies diseases of hematopoietic cells (see below). In the United States, hematopathology is a board certified subspecialty (American Board of Pathology) practiced by those physicians who have completed general pathology residency (anatomic, clinical, or combined) and additional fellowship training in hematology.

Hematopoietic cells originate from the bone marrow and contribute the cellular components of blood including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (megakaryocyte-derived bodies). Additionally, leukocytes contribute significantly to the cellular composition of lymph nodes, the spleen, the thymus, and mucosa associated lymphoid tissues, and are present to some degree in all tissues. Diseases of the hematopoietic system generally manifest as decreases (anemia) or increases (lymphoma/leukemia) in these cell types. Consequently, hematopathologists most frequently evaluate peripheral blood smears, bone marrow

Bone marrow

Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

 aspirates and biopsies

Biopsy

A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

, and lymph nodes biopsies to determine the nature of hematopoietic disease. The hematopathologist incorporates traditional microscopy

Microscopy

Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...

 with ancillary techniques including general laboratory values, immunohistochemistry

Immunohistochemistry

Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...

, flow cytometry

Flow cytometry

Flow cytometry is a technique for counting and examining microscopic particles, such as cells and chromosomes, by suspending them in a stream of fluid and passing them by an electronic detection apparatus. It allows simultaneous multiparametric analysis of the physical and/or chemical...

, and molecular diagnostic tests to make the most accurate diagnosis

Medical diagnosis

Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...

. The hematopathologist works closely with the hematologist/oncologist specialty doctor

Physician

A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 who sees the patient

Patient

A patient is any recipient of healthcare services. The patient is most often ill or injured and in need of treatment by a physician, advanced practice registered nurse, veterinarian, or other health care provider....

 and decides on the best treatment based upon the diagnosis

Medical diagnosis

Medical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...

 made by the hematopathologist.

Diseases of Hematopoietic Cells

Diseases of the hematopoietic system are myriad and include hereditary and congenital disorders as well as acquired disorders. Hereditary and congenital disorders include, in part, bone marrow failure syndromes and primary immune deficiency syndromes. Acquired disorders may be related to nutritional deficiencies (such as iron, folate, and B12 deficient anemias), infectious processes or neoplastic disorders (cancers). Diagnostic criteria and classification guidelines for the neoplastic diseases are codified in the WHO Classification of Tumours of the Hematopoietic and Lymphoid Tissue, most recently revised in 2008. The neoplastic diseases of hematopoietic cells fall into two broad categories, myeloid neoplasms and lymphoid neoplasms. Histiocytic and dendritic cell neoplasms are considered separately.

– Myeloid Neoplasms:
Myeloproliferative neoplasms
Myeloid and lymphoid disorders with eosinophilia
Myeloproliferative/myelodysplastic neoplasms
Myelodysplastic syndromes
Acute myeloid leukemia and related precursor neoplasms
Acute leukemia of ambiguous lineage
– Lymphoid Neoplasms
Precursor lymphoid neoplasms
Mature B-cell neoplasms
Mature T-cell neoplasms
Hodgkin lymphoma
Immunodeficiency associated lymphoproliferative disorders
– Histiocytic and Dendritic Cell Neoplasms

Each category contains several recognized diagnostic entities resulting in nearly 100 different types of hematopoietic cancer, each with defining morphology, pathobiology, treatment, and/or prognostic features. Correct classification, as well as identification of additional factors that may influence prognosis or response to chemotherapy, is essential to allow optimal treatment by the hematologist/oncologist. The hematopathologist is also responsible for additional studies performed after initiation of therapy to monitor for continued remission or disease relapse.