Hematology & Oncology

Hematology is the study of blood. Hematologists specialize in the diagnosis and treatment of blood and blood-related disorders. Oncology is the study of cancer and the diagnosis and treatment of various forms of cancer. They are related in several ways and, hence, are generally taught together. Leukemias are a form of cancer involving blood cells. Since the circulatory system is the mechanism for metastasis (spreading of cancer cells) to other regions of the body, it is important for detection of such cells in the blood.

Anemia

Anemia is an inadequate number of RBC's or hemoglobin content caused by blood loss, deficient erythropoiesis, excessive hemolysis, or a combination of these changes. Symptoms of anemia include pallor (paleness), fatigue, dyspnea, and rapid heart rate. Some of the more commonly known anemias are:

Blood loss: an acute form of anemia caused by hemorrhage.
Aplastic: caused by an injury to or destruction of the bone marrow, resulting in reduced or absent production of RBCs.
Pernicious: caused by a lack of intrinsic factor, which prohibits absorption of vitamin B12, which results in the formation of unusually large and too few RBCs.
Iron Deficiency: results from an inadequate supply of iron needed to form hemoglobin.
Sickle Cell: a chronic, inherited disease that results in the production of abnormal, crescent shaped erythrocytes that carry less oxygen, break easily, and block blood vessels. It occurs almost exclusively among African Americans.

Transfusion

At least 15 million transfusions are given every year in the U.S.. Before a transfusion, the donor blood must be tested to determine its suitability for transfusion and compatibility with the recipient's blood. Testing includes ABO and Rh typing, antibody screening, and testing for infectious disease markers, including syphilis, hepatitis B surface and other antigens, and antibodies against various viruses (e.g., HIV, hepatitis C, etc.).

Myeloproliferative Disorders

This is a group of disorders characterized by abnormal proliferation of one or more hemopoietic cell lines or connective tissue elements. The disorders include:

polycythemia vera: an idiopathic chronic disorder characterized by an increase in Hb concentration and RBC mass (erythrocytosis).
myelofibrosis: an idiopathic chronic disease characterized by bone marrow fibrosis, splenomegaly, and leukoerythroblastic anemia with teardrop-shaped RBCs.
chronic myelogenous leukemia: a disease characterized by overproduction of granulocytes.
primary thrombocytopenia: a disease characterized by an increased platelet count, megakaryocytic hyperplasia, and a hemorrhagic or thrombotic tendency.

Hemophilia

Hemophilia is an inherited bleeding disorder caused by a shortage of a clotting protein in the plasma. It occurs almost exclusively in males. Treatment involves transfusing whole blood or plasma, and administering the missing protein factor.

Thrombosis

Normally, blood clotting occurs to prevent blood loss in an injured blood vessel. Blood clots can form in an intact vessel that contains fatty deposits or one that is inflamed. These clots, known as thrombi, cause pain and may damage the tissues served by the vessel. They can be fatal in some cases. Anticoagulants such as warfarin and heparin help inhibit the further growth of the thrombi and prevent new clots from forming.

Newly formed thrombus in celiac artery superimposed on atherosclerosis and thrombosis.

Embolism

An embolism occurs when particles traveling in the bloodstream lodge in a vessel away from their point of origin. These fragments may be a whole or partial thrombus, or may be composed of atheromatous debris, cholesterol crystals, air, or fat from the marrow of fractured bones. If drugs do not inhibit or dissolve clots, surgery may be indicated. Thrombi often form in the leg veins due to sluggish blood flow, injuries, recent surgery, or prolonged immobility. If an embolus travels through the heart to a pulmonary artery, it may create an obstruction, a condition known as pulmonary embolism, which deprives lung tissue of vital oxygen and lead to death.

Right pulmonary artery embolism in 43 year-old woman shown in left angiogram with arrow. Right picture following a 2-hour infusion of tissue plasminogen activators demonstrates significant resolution of thrombus.

Blood Cell Disorders

There are numerous disease of the blood involving various blood cells. Some of these diseases are:

Thrombocytopenia: platelet count below the normal count (140,000-440,000/microliter).
Leukopenia: WBC count below 4000/mcL).
Neutropenia: low neutrophil count (< 1000/mcL).
Lymphocytopenia: total lymphocyte count below 1000/mcL (adults) or 3000/mcL (children).
Eosinophilia: peripheral eosinophil count > 350/mcL.

Leukemias

Leukemia is a malignant disease of the bone marrow or lymph tissue. It results in a high number of malignant, immature white blood cells invade organs elsewhere in the body. There are several types of leukemias which may be classified into:

acute: rapidly progressing leukemias caused by replacement of normal bone marrow by blast cells of a clone arising from malignant transformation of a hemopoietic stem cell. Acute leukemias are either lymphoblastic or myelogenous.
chronic: overproduction of lymphocytes or granulocytes, particularly in the bone marrow.

Symptoms of leukemia include fever, pallor, swelling of lymphoid tissues, fatigue, anemia, bleeding gums, excessive bruising, and joint pain. Treatments include chemotherapy, corticosteroids, radiation, and/or bone marrow transplant. Treatments have not been proven to prolong survival however, overtreatment is more dangerous and likely to shorten expected lifespan in leukemia patients compared with undertreated patients.

Hodgkin's Disease

An idiopathic disease, Hodgkin's is characterized by localized or disseminated tumor cells that arise primarily from lymph node tissues and bone marrow. Symptoms vary depending on the stage of progression and tissue involvement but may include pain, paraplegia, laryngeal paralysis, leg edema, and dyspnea. Chemotherapy or radiotherapy are often successful.

Mixed cells in Hodgkin's disease.

Cancer

Cancer is a localized growth caused by uncontrolled cell reproduction which can spread, if untreated, to other parts of the body. Besides imaging, bone scans, mammography, sputum cytology, and laboratory tests are used to help detect cancer. Various cancer antigens which are tumor-associated serum markers are available for staging some forms of cancer and monitoring its treatment. Blood levels of calcitonin, carcinoembryonic antigen, acid phosphatase, and estrogen receptor assays may indicate various forms of cancer. The major forms of treatment for cancer are surgery and radiotherapy for local and regional forms of cancer. For systemic cancers, chemotherapy is the primary form of treatment. Other forms of cancer therapy include endocrine therapy for certain cancers such as prostate, liver, breast, and endometrium; immunotherapy, and thermotherapy.