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Anatomical pathology

Anatomical pathologists diagnose disease by examining tissue removed from living patients either by biopsy or during surgery. For example, if you have a biopsy of a breast lump or an unusual skin mole, it is the anatomical pathologist who makes the diagnosis. Tissue is carefully studied using a microscope and special testing, such as molecular tests, may be required. The diagnosis and other features of the disease are documented in a pathology report that your doctor will use to determine the probable course of the disease and the most effective treatment. Anatomical pathologists also provide urgent interpretation of small tissue samples that are removed during an operation and rushed to the pathologist’s laboratory. The pathologist helps guide the surgeon to determine how extensive the surgery needs to be. Sometimes samples are even smaller specimens of separated cells (cytopathology). A large part of an anatomical pathologist’s role is the detection and diagnosis of cancer. A tissue diagnosis is essential before starting any treatment involving major surgery, radiation or drugs, treatments that may have major side effects. Anatomical pathologists also perform autopsies to determine the extent of disease and to establish the cause of death.

General pathology

General pathologists are a “Jack of all trades”, combining anatomical pathology with expertise in the clinical branches of laboratory medicine: clinical chemistry, microbiology, hematology and blood banking, though not in as much detail as specialists in each of these disciplines.  General pathologists are consulted daily by patients’ physicians with questions about what tests to order and how to interpret the test results. General pathologists often practice in smaller hospitals and in more rural settings where a broad knowledge of disease is required.

Hematopathology

Hematopathologists are experts in diseases of the blood, bone marrow, and lymph nodes.  They analyze blood components, such as blood count, and blood and bone marrow cells to help diagnose disease such as anemia, lymphoma, hemophilia, blood-clotting disorders, and leukemia. Hematopathologists also manage blood transfusion services.  These include blood products such as red blood cells or platelets that are often urgently required by patients during surgery or in the emergency room following trauma, such as a car accident.

Medical biochemistry

Medical biochemists are medical doctors who help diagnose disease by examining body fluids or tissues for abnormal levels of substances such as electrolytes, proteins, enzymes, and hormones. For example they assess levels of iron in the blood, measure levels of enzymes released into the blood after a heart attack to help in the diagnosis, and measure certain proteins produced by cancers to monitor the response to treatment. Medical biochemists work together with clinical chemists and other scientists who are experts in this branch of laboratory medicine. Medical biochemists also measure body fluid levels of therapeutic and illicit drugs, and of poisons.

Medical microbiology

Medical microbiologists are experts in infectious disease. They analyze and interpret tissue, blood and body fluids to identify microorganisms that can cause infections – bacteria, viruses, fungi, and parasites – so the patient can receive the most effective treatment. Working closely with their clinical colleagues, they also play a role in the control of infectious disease. As many new infectious diseases have emerged (e.g. HIV, Hepatitis C, new flu viruses, SARS) and “old” infections such as tuberculosis and malaria have become resistant to treatment, medical microbiologists have taken a lead role in research, diagnosis, and treatment of these often life-threatening infections. Many bacterial infections have become resistant to antibiotic treatment, and microbiologists test these bacteria to determine the best antibiotic to use. This assessment of antibiotic resistance now involves highly advanced testing and genetic analysis. Recent advances in technology (e.g. automation) and molecular medicine have added greatly to the medical microbiologist’s diagnostic resources. At the same time however, microbiology remains a ‘hands-on’ discipline.

Forensic pathology

Forensic pathologists are anatomical pathologists who specialize in autopsy pathology and focus on the medicolegal aspects of sudden or unexpected death. They identify the cause of death, reconstruct the circumstances by which the death occurred, and work closely with the police in criminal cases. These are the pathologists you see helping solve cases on popular TV crime shows.

Immunopathology

Immunopathologists analyze and interpret tissue, blood and body fluid samples for immune responses associated with disease. In the laboratory, these pathologists design, perform and supervise tests of the immune system. They provide advice on a wide variety of other disorders including recurrent miscarriage and some areas of transplantation medicine. They can also assist with the management of autoimmune diseases, including AIDS.

Genetic pathology

Genetic pathologists are experts in interpreting the results of laboratory genetic tests. By studying disease at the molecular level (chromosomes and DNA) genetic pathologists make clinical diagnoses, determine disease prognosis, monitor infections and therapies, and provide risk assessments for genetic diseases. They play a pivotal role in providing patients who have genetic diseases or cancer with specialized advice on prevention, care and treatment. There are two main branches of laboratory genetics:

• Clinical cytogenetics – involves the microscopic analysis of chromosomes. These techniques are used to diagnose such conditions as Down Syndrome and certain types of cancer, e.g. leukemia and sarcoma.
• Molecular genetics – uses the tools of DNA technology to analyze mutations (changes) in genes. Many gene mutations have been identified that are associated with such diseases as cystic fibrosis, breast cancer and diabetes mellitus.

Molecular Pathology

A molecular pathologist is often also a specialist in another pathology discipline such as anatomical pathology, hematopathology, or medical microbiology. They focus on understanding the molecular abnormalities that cause disease, and assess new markers of disease progression and response to treatment. Molecular pathology is commonly used in the diagnosis of cancer and infectious diseases. The molecular pathologist plays the most important role in personalized medicine, providing a unique fingerprint of an individual’s disease that allows doctors to treat conditions such as cancer on a personal, or individual basis, with therapy designed specifically for that patient.

Content source: The Royal College of Pathologists of Australasia, with permission.