What is a pathology test?
Pathology is still the gold standard for the diagnosis of cancer, meaning it has been the most important diagnostic tool to date. A pathologist is a physician specializing in the diagnosis of disease based on examination of tissues and fluids removed from the body. Pathology tests involve evaluation of a small sample of cells under a microscope to determine whether they are cancerous by identifying structural abnormalities.
How are tissue samples obtained?
Most cancer patients will undergo a biopsy or other procedure to remove a sample of tissue for examination by a pathologist in order to diagnose their disease. There are a variety of methods used to obtain samples, including a typical biopsy, fine needle aspiration, or a biopsy with the use of an endoscope. The method used to gain a tissue sample depends on the type of mass and location in the body.
A typical biopsy involves the surgical removal of a mass of abnormal cells. Fine needle aspiration involves guiding a thin needle into the cancer and gently sucking out cells for microscopic evaluation. An endoscope is a lighted tube that can be guided into the body through an orifice, such as the mouth or anus, and is used to perform a biopsy. It allows the physician to see the cells in question and then “scrape” the abnormal cells in order to get a sample. For example, throat cells may be sampled in this way.
A physician may also perform a bone marrow biopsy, which uses a large needle to remove a sample of the bone marrow. The purpose of this procedure is to diagnose lymphoma and leukemia or determine whether certain types of cancer, such as breast or prostate, have spread to the bones. Bone marrow biopsies are usually performed in the bones of the rear hip. This procedure may also be called a bone marrow aspiration.
Once a tissue sample is obtained, it is then “fixed”, meaning it is treated in a way that stops degradation and prevents the cells in the sample from changing characteristics. Next, the sample is stained so that the pathologist can see the cell structure under a microscope and determine whether the cells are exhibiting cancerous characteristics.
The Pathology Report
Once a tissue sample is obtained, the pathologist will examine the tissue sample under the microscope in order to determine if it contains normal, pre-cancerous or cancerous cells. The pathologist then writes a pathology report summarizing his or her findings.
The pathology report is a critical component of the diagnostic process. The primary doctor will use this report in conjunction with other relevant test results to make a final diagnosis and develop a treatment strategy.
After any biopsy or excision, you should request a copy of the pathology report for your records so that you have documentation of your pathologic diagnosis. In addition, it is helpful to have a copy of the pathology report to refer to when you are researching your disease.
By having a basic understanding of what the pathologist is looking for and the structure of the report, you may better understand your pathology report. Having a copy of your pathology report for your personal records is highly recommended. Your primary doctor should be able to address specific questions you have about your pathology report.
Understanding your Pathology Report
Although pathology reports are written by physicians for physicians, you may be able to decipher some of the medical jargon provided by the report. Your primary doctor should be able to address specific questions you have about your pathology report; however, it is helpful to have a basic understanding of what the pathologist is looking for. The structure and information provided in your pathology report may vary, but the following sections are usually included.
Demographics: This section includes the patient’s name and date of procedure. You should check that this information is correct to ensure that you have the correct pathology report.
Specimen: The specimen section describes the origin of the tissue sample(s).
Clinical History: The clinical history section provides a brief description of the patient’s medical history relevant to the tissue sample that the pathologist is examining.
Clinical Diagnosis (Pre-Operative Diagnosis): The clinical diagnosis describes what the doctors are expecting before the pathologic diagnosis.
Procedure: The procedure describes how the tissue sample was removed.
Gross Description (Macroscopic): The gross description refers to the pathologist’s observations of the tissue sample using the naked eye. It may include size, weight, color or other distinguishing features of the tissue sample. If there is more than one sample, this section may designate a letter or number system to distinguish each sample.
Microscopic Description: In the microscopic description, the pathologist describes how the cells of the tissue sample appear under a microscope. Specific attributes that the pathologist may look for and describe may include cell structure, tumor margins, vascular invasion, depth of invasion and pathologic stage.
Cell Structure: Using a microscope, the pathologist examines the cell structure and microscopic attributes of the tissue sample and assigns a histologic grade to the tumor. The histologic grade helps the pathologist identify the type of tumor. The grade may be described numerically with the Scarff-Bloom-Richardson system (1-3) or as well-differentiated, moderately-differentiated or poorly differentiated.
* Grade 1 or well-differentiated: Cells appear normal and are not growing rapidly.
* Grade 2 or moderately-differentiated: Cells appear slightly different than normal.
* Grade 3 or poorly differentiated: Cells appear abnormal and tend to grow and spread more aggressively.
Tumor Margins: If cancerous cells are present at the edges of the sample tissue, then the margins are described as “positive” or “involved.” If cancerous cells are not present at the edges of the tissue, then the margins are described as “clear,” “negative” or “not involved.”
Vascular Invasion: Pathologists will describe whether or not blood vessels are present within the tumor.
Depth of Invasion: The depth of invasion may not be applicable to all tumors, but is used to describe invasion of the tumor.
Pathologic Stage: The clinical stage is determined from the pathologic stage as well as other diagnostic tests such as X-rays. The pathologic stage, designated with a “p,” describes the extent of the tumor as determined from the pathology report only. The staging system most often used by pathologists is based on the American Joint Commission on Cancer’s (AJCC) TNM (tumor, node invasion, metastasis) system.
Special Tests or Markers: Depending on the tissue sample, the pathologist may conduct tests to further determine whether or not specific proteins or genes are present, as well as how fast cells are growing.
Diagnosis (Summary): The final diagnosis is the section where the pathologist compiles the information from the entire pathology report into a concise pathologic diagnosis. It includes the tumor type and cell of origin.
Pathologist Signature: The report is signed by the pathologist responsible for its contents.