What is Histopathology and Cytopathology?

What is histopathology and why is it important?

"Anatomic" pathology comprises the examination of cells, tissues or whole organs from patients by "anatomic" pathologists to determine whether these specimens are normal or abnormal, and if abnormal, to diagnose the condition causing the abnormality.

The specimens for examination are obtained from patients by their specialist or GP, and transferred to TissuPath for study. These specimens can be small (as in skin or prostate biopsies) or large (as in the surgical removal of a kidney, a prostate gland or part of the colon).

Pathologists with special training in histopathology ("histopathologists"), such as those working at TissuPath, first examine the specimen by eye, to see if there are any obvious abnormalities and to select portions of the specimen, if it is large, for microscopic analysis.

TissuPath's pathology scientists prepare the tissues for microscopic analysis by ensuring that they are "fixed" (usually with formaldehyde), "processing" them to remove the fixative and water, and then "embedding" them in a small block of paraffin wax.

Thin "sections" of the tissue samples are then sliced from the paraffin blocks with a special mechanical knife (a "microtome").

The sections are then put on microscope slides and stained so the tissues and the component cells are easily visible under the microscope. One or two of TissuPath's histopathologists who are experts in the type of tissue being analyzed (skin, colon, prostate, etc) then examine the sections in detail with a microscope. Their findings are then reported back to the doctor in writing. If the findings are unusual, or require urgent action, we will often phone the doctor as well.

Sometimes the microscopic examination will be equivocal (as to whether it is normal or not, and if abnormal, as to the specific diagnosis). In this case we assess the tissue sections for expression of specific marker proteins by "staining" them with specific antibodies, in a process called "immunohistochemistry" or IHC. We may also look for deletions of specific chromosomes by FISH testing as this may also aid in diagnosis in some cases.

Why is histopathology important?
Analysis of cells or tissues from patients with signs or symptoms suggesting illness is often essential to making a correct diagnosis. And of course, the proper course of therapy cannot be planned without a correct diagnosis.

The opinion of the pathologist is essential, in virtually every instance, for making a diagnosis of cancer. It would be a tragedy if a biopsy of cancer was misread as being normal (as proper therapy would not be initiated), or if a biopsy of a benign lesion or normal tissue was misread as showing cancer, as inappropriately aggressive treatment might well be undertaken.

For this reason, TissuPath pathologists largely restrict their practice to conditions where they have well-established, specific expertise. Just as specialist physicians or surgeons are often important for proper management of specific diseases, specialist pathologists are critical to making correct diagnoses when dealing with specific organs or tissues.

Prostate cancer is a very good example of a disease that requires specialist pathology, "uropathology", for accurate diagnosis.