Pathologist: Definition

by Jason Wasserman MD PhD FRCPC
March 19, 2026

A pathologist is a medical doctor who specializes in diagnosing disease by examining tissues, cells, and body fluids — usually under a microscope. When you have a biopsy or surgery, the tissue removed is sent to a pathologist, who studies it and writes the pathology report that explains what was found. In most cases, the pathologist is the doctor who actually establishes your diagnosis — even though you will likely never meet them in person. Their work is the foundation on which your treatment plan is built.

What does a pathologist do?

Pathologists are responsible for examining tissue and cell samples and turning what they see into a clear diagnosis. Their work includes:

Examining tissue samples — pathologists study specimens (the tissue or fluid removed during a procedure) both with the naked eye and under a microscope to identify disease.
Making the diagnosis — based on what they see, pathologists determine whether tissue is normal, benign (not cancer), or malignant (cancer), and they identify the specific type of disease present.
Ordering and interpreting additional tests — when the diagnosis is not clear from the microscope alone, pathologists order specialized tests such as immunohistochemistry and molecular testing and interpret the results.
Writing the pathology report — pathologists summarize their findings in a written report that guides the rest of your medical team in planning treatment.
Advising other doctors — pathologists frequently discuss complex cases with surgeons, oncologists, and other specialists to help guide patient care.

How does a pathologist make a diagnosis?

The process of reaching a diagnosis usually involves several steps:

Gross examination — when a specimen first arrives in the laboratory, the pathologist examines it with the naked eye, recording its size, color, and appearance, and selecting small pieces for closer study. This is described in the gross description section of the report.
Microscopic examination — the selected tissue is processed, cut into very thin slices, placed on glass slides, and stained — most often with hematoxylin and eosin (H&E), dyes that add color and contrast so the cells can be seen clearly. The pathologist then examines these slides under a microscope.
Additional testing — if needed, the pathologist orders further tests to confirm the diagnosis, identify the specific disease type, or look for features that guide treatment.
Reaching a conclusion — the pathologist combines all of this information — along with the clinical history provided by the treating doctor — to reach a final diagnosis, which is recorded in the pathology report.

Are there different types of pathologists?

Pathology is a broad field, and many pathologists focus on a particular area:

Anatomical pathologists — diagnose disease by examining tissue samples from biopsies and surgeries. This is the type of pathologist who most often writes the reports patients receive.
Cytopathologists — specialize in diagnosing disease from individual cells rather than larger tissue samples, such as cells collected during a Pap test or a fine needle aspiration.
Hematopathologists — specialize in diseases of the blood, bone marrow, and lymph nodes, including leukemia and lymphoma.
Neuropathologists — specialize in diseases of the brain, spinal cord, and nerves.
Forensic pathologists — investigate the cause of death, often in a legal context.

Some pathologists also focus on specific organ systems, such as the skin (dermatopathology) or the digestive tract (gastrointestinal pathology). When a case is complex, it may be reviewed by a pathologist who subspecializes in that particular area.

Can a pathologist examine tissue during surgery?

Yes. In some operations, the surgeon needs an answer before the surgery is finished — for example, to confirm a diagnosis or to check whether all of a tumor has been removed. In these situations, a pathologist performs a frozen section, a rapid examination in which tissue is quickly frozen, cut, stained, and examined under a microscope within minutes. The pathologist then communicates the result directly to the surgical team while the operation is still underway.

Can I speak with the pathologist who examined my tissue?

Although patients rarely meet the pathologist, it is often possible to speak with them or request a review of your case. If you have questions about your pathology report, the best first step is usually to ask your treating doctor, who can contact the pathologist on your behalf. In some cases, patients can request a direct conversation with the pathologist, or ask for the slides to be sent for a second opinion at another institution. Second opinions are a routine and accepted part of medicine, particularly for rare or difficult diagnoses.

Questions to ask your doctor

Which pathologist made my diagnosis, and was the case reviewed by a subspecialist?
Can I speak with the pathologist or request a review of my pathology report?
Would a second opinion on my pathology be helpful in my situation?