What Is a Pathologist? The Doctor Behind Your Diagnosis

Section Editor: Jason Wasserman MD PhD FRCPC
November 6, 2026

A pathologist is a medical doctor who diagnoses disease by examining tissue, cells, and body fluids. When doctors remove tissue or cells from your body for testing, a pathologist usually interprets the results. Most patients never meet their pathologist, yet the pathologist’s report often determines the diagnosis. It also shapes what treatment your care team will consider.

This article explains who pathologists are and what they do with your sample. It describes the different kinds of pathologists, how they are trained, and how they work with the rest of your care team. It also explains how you can speak with a pathologist about your own report.

What does a pathologist do?

A pathologist’s main job is to make a diagnosis from a sample taken from your body. The sample might be a small biopsy or a whole organ removed during surgery. It might also be a few cells from a Pap test or a blood sample. The pathologist studies it and writes a pathology report that names the disease and describes its important features.

Pathologists are sometimes called “the doctor’s doctor.” Your surgeon, oncologist, or family doctor asks the question, and the pathologist provides the answer. A surgeon may ask whether a lump is cancer. An oncologist may ask whether a cancer carries a change that a targeted drug can act on. The pathologist answers by examining the tissue directly.

For cancer, the pathology report does much more than say yes or no. It describes the type of cancer, its grade, and its size. It also reports whether the cancer has spread to lymph nodes and whether it was completely removed. These findings set the stage and guide the treatment choices your team will discuss with you.

What happens to your sample in the pathology laboratory?

A pathologist begins working on your sample the moment it arrives in the laboratory. The lab checks each sample against your name and your doctor’s request. It is then given a unique number that follows every piece of tissue and every slide made from it.

Gross examination. The tissue is first examined with the naked eye. A pathologist or a pathologist’s assistant measures it, describes it, and cuts the most important areas into small pieces. This step is recorded in the gross description of your report.
Processing. The small pieces are placed in cassettes and treated overnight so they can be embedded in wax. The wax holds the tissue firm enough to cut into extremely thin slices.
Making slides. A histotechnologist cuts slices thinner than a human hair and places them on glass slides. The slides are stained with hematoxylin and eosin, which colors cell nuclei purple and most other structures pink.
Microscopic examination. The pathologist examines every slide under the microscope. This is where most diagnoses are made, and it is described in the microscopic description section of some reports.
Additional tests. The pathologist may order special stains, immunohistochemistry, or molecular testing to answer questions the routine slides cannot.
The report. The pathologist writes the final diagnosis and signs the report. Once it is signed, it is sent to your doctor and often to your patient portal.

This process usually takes a few days for a biopsy and longer for a large surgical specimen. Our article on how long pathology results take explains why some results take longer than others.

How does a pathologist make a diagnosis?

A pathologist makes a diagnosis by recognizing patterns in how cells look and how they are arranged. Normal tissues have a predictable structure, and disease changes that structure in ways a trained pathologist can recognize, much as an experienced reader recognizes handwriting.

The pathologist looks at cell size and shape, the appearance of their nuclei, and how quickly they appear to be dividing. They also look at how the cells relate to the surrounding tissue. For example, cancer often grows into tissue where it does not belong, a process called invasion.

The microscope is not the only source of information. The pathologist reads the clinical history your doctor provides, including your symptoms and imaging results. A finding that is harmless in one setting can be worrying in another, so this context matters.

When a case is difficult, the pathologist gathers more evidence. They may order additional stains, cut deeper into the tissue, or consult a colleague. Sometimes the honest answer is that a diagnosis cannot be made with certainty from the sample available. In that case, the report says so and explains what would help.

What are the different kinds of pathologists?

Pathology is a broad specialty, and many pathologists focus on one area of the laboratory or one part of the body. The pathologist who signs your report may be a general pathologist or a subspecialist with additional training. The main kinds are:

Anatomical or surgical pathologist. Examines tissue removed by biopsy or surgery. This is the pathologist behind most of the reports explained on this site.
Cytopathologist. Examines individual cells rather than tissue samples, such as a Pap test or a fine needle aspiration. Our article on the cytology report explains this work.
Hematopathologist. Diagnoses diseases of the blood, bone marrow, and lymph nodes, including leukemia and lymphoma.
Clinical pathologist. Oversees laboratories that run blood tests, blood transfusions, and infection tests. In Canada, some of this work is done by separate laboratory specialists, such as medical microbiologists.
Molecular or genetic pathologist. Interprets tests that look for changes in DNA and RNA, such as next-generation sequencing.
Neuropathologist. Specializes in diseases of the brain and spinal cord, and often of nerves and muscle as well.
Dermatopathologist. Specializes in skin biopsies, such as moles, rashes, and skin cancers. A skin biopsy is often sent to a dermatopathologist when the diagnosis is difficult.
Pediatric pathologist. Specializes in diseases of infants and children, including childhood tumors.
Forensic pathologist. Performs autopsies to determine the cause and manner of death, often for a coroner or medical examiner.

Within surgical pathology, many pathologists also subspecialize by organ system. A breast pathologist, a gastrointestinal pathologist, or a gynecologic pathologist sees many cases from one part of the body. In larger hospitals, your sample is often sent directly to the pathologist with that focus.

How are pathologists trained?

Pathologists complete the same medical school training as every other doctor. They then spend several more years training full-time in pathology before they can practice independently. This training includes thousands of cases examined under supervision.

In the United States, a pathologist completes four years of medical school and then a pathology residency. Combined training in anatomic and clinical pathology takes four years, and training in one of these alone takes three. Pathologists are then certified by the American Board of Pathology—many complete one or two more years of fellowship in a subspecialty.

In Canada, residency in anatomical pathology lasts five years after medical school. Related specialties, such as general pathology and neuropathology, have their own training programs. Pathologists who complete this training and pass the national examinations become Fellows of the Royal College of Physicians and Surgeons of Canada. The letters FRCPC after a pathologist’s name show this certification.

Training does not stop at certification, and pathologists must keep learning throughout their careers to stay certified. Disease classifications change often, and new tests are added every year.

Who else works in the pathology laboratory?

A pathologist leads a team, and many skilled professionals handle your sample before the pathologist sees it. Each plays a part in ensuring an accurate diagnosis.

Pathologists’ assistants. These professionals perform the gross examination of surgical specimens under a pathologist’s supervision. They usually hold a two-year master’s degree and a professional certification.
Histotechnologists. They process tissue, cut thin sections, and prepare and stain glass slides.
Cytologist. They screen cytology samples, such as Pap tests, and mark abnormal cells for the pathologist to review.
Medical laboratory scientist. They run blood tests, infection tests, and molecular tests, and check the instruments for accuracy.

How does a pathologist work with the rest of your care team?

Pathologists work closely with the surgeons and oncologists caring for you, even though patients rarely see this part of their work. The pathologist often talks with your care team before, during, and after your report is issued.

During some operations, the surgeon needs an answer before the operation ends. The pathologist can freeze a piece of tissue, cut it, and examine it within minutes. This is called a frozen section. The College of American Pathologists expects 90% of simple frozen sections to be completed within 20 minutes.

Pathologists also participate in tumor boards, regular meetings where specialists review a case together and agree on a plan. The pathologist shows the slides, explains the diagnosis, and answers questions about the findings. When a result is urgent or unexpected, the pathologist usually calls your doctor directly rather than waiting for the report to be read.

How do pathologists make sure the diagnosis is right?

An accurate diagnosis is the foundation of good treatment, and pathology laboratories use several safeguards to protect it. Laboratories are inspected and accredited, and they take part in regular testing programs that check their accuracy.

Many laboratories have a second pathologist review new cancer diagnoses and difficult cases before signing the report. When a case is unusual, the pathologist may send it to an expert at another center. This is called a consultation, or a second opinion. You can also ask your doctor to request a second opinion on your own slides.

Reports can be updated after they are signed. An addendum adds new information, such as the result of a test that finished later. An amendment changes something in the original report. Both help keep the record complete and accurate.

Can I talk to the pathologist about my report?

Most patients hear about their pathology results from the doctor who ordered the test, not from the pathologist. That doctor knows your full history and can explain what the result means for your care. They can also contact the pathologist if a question about the report needs an expert answer.

Some hospitals now offer programs that let patients meet the pathologist who examined their sample. At the Sylvester Comprehensive Cancer Center in Miami, for example, a pilot program lets patients with breast biopsies meet a pathologist in person or by video. Some patients review images of their own slides during these visits.

If no such program exists where you are treated, you can ask your doctor whether the pathologist could answer a specific question. For help with the terms in your report, you can also ask Osler, our pathology assistant. Osler cannot see your medical records, so your doctor remains the best person to explain what your result means for your care.

How is pathology changing?

Pathology is changing quickly, and pathologists now handle some of the most advanced tests in medicine. Many cancer reports include molecular results that help decide whether a targeted drug or immunotherapy may be considered. Interpreting these results is now routine in a pathologist’s work.

Many laboratories now scan glass slides into high-resolution digital images. The pathologist can then examine the slide on a computer screen instead of a microscope. In 2017, the US Food and Drug Administration (FDA) first cleared a digital pathology system for making diagnoses. Digital slides also make it easier to share a difficult case with an expert in another city.

Computer programs, including artificial intelligence tools, are beginning to help pathologists with tasks such as counting cells or flagging suspicious areas. These tools assist the pathologist rather than replace them. The pathologist still reviews the slides, considers your clinical history, and takes responsibility for the diagnosis.

Questions to ask your doctor

Who was the pathologist who examined my sample?
Did a pathologist who specializes in this type of disease examine my sample?
Did a second pathologist review my diagnosis before signing the report?
Were any special stains or molecular tests done on my sample?
Are any tests on my sample still pending?
Was my case discussed at a tumor board?
Would a second opinion from an expert pathologist be helpful in my case?
How would I arrange to have my slides sent for a second opinion?
Does this hospital offer a way for patients to meet the pathologist?
Has my report had an addendum or an amendment since it was first issued?