What Does a Pathologist Do?

Pathologists, also known as medical pathologists, are physicians who are trained to investigate the cause and effect of diseases or injuries. They do this through the analysis of organ, tissue, blood, or body fluid samples.

Pathologists are broadly classified as either anatomical or clinical pathologists. Anatomical pathologists perform visual, microscopic, and molecular analyses of tissues, organs, and whole bodies (such as during an autopsy). Clinical pathologists diagnose disease based mainly on lab analyses of blood, urine, and other body fluids.

This article discusses pathologists, what they do, and what type of training they receive.

What Is a Pathologist?

Medical pathology is a field of medicine where practitioners identify the cause and effect of illness. Pathology is not limited to a single disease, population, or organ system.

Pathologists are often considered "doctor's doctors" because they assist doctors in making diagnoses and treatment decisions.

There are two categories of pathologists: Anatomical and clinical. Although both types work in similar environments and have similar diagnostic goals, there are key differences between them.

• Anatomical pathologists conduct tests to determine the specific cause of a disease. They center their investigations on tissues and organs. Historically, the practice was devoted to post-mortem investigations but today it includes a variety of procedures to diagnose diseases like cancer based on the analyses of surgical specimens. The work of anatomical pathologists has a more direct impact on patient care.
• Clinical pathologists diagnose disease based on the analysis of body fluids or cells obtained from tissue extracts. Clinical pathology tests such as a complete blood count, urinalysis, blood glucose test, and throat culture are familiar to most people. Compared to anatomical pathologists, clinical pathologists perform more routine tests that aid rather than direct a diagnosis. Individually, the test results have less of a direct impact on patient care.

Pathologists who practice both anatomical and clinical pathology are known as general pathologists.

What Do Pathologists Do?

Because their roles and functions are so distinctive, anatomical and clinical pathologists rely on different tools and techniques. Although there will be some overlap in procedures (particularly molecular and genetic testing), many of the tools used are specific to the specimens being analyzed.

Anatomical Pathology

Anatomical pathologists start with a visual examination of an organ or tissue sample. They then proceed to microscopic analysis, often followed by molecular analysis. Common procedures include:

• Gross examination, the examination of diseased tissue with the naked eye, a magnifying glass, or a standard light microscope
• Cytopathology, the examination of tissues at the cellular level, including tissues and cells obtained through biopsy or fine needle aspiration (FNA)
• Histopathology, the microscopic examination of specially stained tissues to identify normal and abnormal structures in a cell and/or tissue
• Electron microscopy, a high-powered microscope lets the pathologist see structures inside of a cell
• Immunohistochemistry, the use of immune proteins (called antibodies) that, when matched to receptors on cells (called antigens), can help identify cancer and certain viral infections
• Fluorescence in situ hybridization (FISH), a technique in which RNA or DNA is matched to corresponding DNA or RNA in a specimen to identify cancers or chromosome abnormalities
• Tissue cytogenetics, identifies chromosome disorders by looking for errors in the genetic sequence
• Flow immunophenotyping, a technique especially useful for leukemia or lymphoma in which a tissue sample is exposed to different antibodies to identify normal and abnormal cell types

Clinical Pathology

A clinical pathologist will usually start with a visual examination of blood, urine, or other body fluids. They will then proceed to a microscopic exam followed by a lab analysis.

Unlike anatomical pathologists, clinical pathologists will run tests based on a physician's suspicion and return results that either support or exclude that suspicion. The procedures can be broadly described as:

• Macroscopic examinations, a visual evaluation of a sample to check for abnormalities, such as color, density, coagulation, and sedimentation
• Microscopic evaluations, using various techniques and stains (such as bacterial gram staining and FISH) to examine a specimen under a microscope
• Automated analyzers ("lab tests"), calibrated equipment that can be used to evaluate specimens and determine whether they fall above, below, or within a normal range (reference range)
• Lab cultures, in which a specimen is applied to a culture medium to grow and positively identify bacterial, fungal, or viral pathogens (disease-causing agents)

Subspecialties

Because the clinical applications of pathology are so vast, it is not uncommon for pathologists to specialize in a specific field of practice.

Among the subspecialties anatomical pathologists commonly pursue:

• Cytopathology, the study of disease on a cellular level
• Forensic pathology, determining causes of death, both natural and unnatural
• Neuropathology, the identification of disease from brain and nerve tissues
• Pediatric pathology, involving conditions of childhood
• Surgical pathology, involving the evaluation of surgical specimens

Among the subspecialties clinical pathologists commonly pursue:

• Blood banking and transfusion medicine, involving the monitoring and processing of blood products
• Chemical pathology, involving the use of lab tests to diagnose and monitor disease
• Clinical microbiology, focused specifically on infectious diseases
• Cytogenetics, the study of the inheritance of chromosomal disorders
• Hematopathology, focused on the evaluation of blood

Many of these specialists will go on to become medical examiners and coroners or to work in genetics labs and medical research facilities.

How to Become a Pathologist

Becoming a pathologist can require 11 to 14 years of education, including four years of college, four years of medical school, and three to four years in a pathology residency program. The majority of pathologists will also pursue training with a one- to two-year fellowship in a pathology subspecialty.

Pathologists must first get a bachelor's degree from an accredited college. They do not need to pursue any specific major but must complete the required pre-medical courses, including biology, physics, English, and social sciences. They also need to take the Medical Competency Aptitude Test (MCAT) a year before graduating, which most medical schools use to select students.

The first two years of medical school are devoted primarily to classroom studies. The second two years include clinical rotations in hospitals and medical facilities to gain broad exposure to the different fields of medicine. Upon graduating, students are awarded a degree as either a doctor of medicine (MD) or a doctor of osteopathic medicine (DO), depending on the medical school.

To begin practicing, prospective pathologists need to obtain a medical license in their state. Licensing requirements vary, but most states require them to pass a national exam and, in some states, an additional state exam.

After attaining a license, prospective pathologists begin a three-year residency program in either anatomical or clinical pathology. There are around 145 accredited programs nationwide. They can also opt to train in a combined four-year program in anatomical and clinical pathology (AP/CP).

Upon the completion of residency, most pathologists will obtain board certification from the American Board of Pathology (ABP) by passing a written and practical exam. Those who do tend to have more job opportunities.

ABP certification must be renewed every 10 years, during which time pathologists must maintain a certain number of study hours by participating in accredited continuing medical education (CME) programs.

Summary

A pathologist is a medical doctor who specializes in analyzing blood, tissue, organs, and bodily fluids to help identify diseases. An anatomical pathologist primarily studies tissues and organs, while a clinical pathologist studies body fluids or cells obtained from tissue. A general pathologist is a pathologist skilled in both areas.

Pathologists use a range of medical equipment and test procedures to look for evidence of specific diseases. A pathology report can help diagnose a specific disease and provide treatment guidance.