Pathology Testing
Pathology is still the most important tool for the diagnosis of cancer. A pathologist is a physician who specializes in the diagnosis of disease based on examination of tissues and fluids removed from the body. Pathology tests for cancer consist of looking at a small sample of cells under a microscope. The pathologist can tell if they are cancerous by identifying abnormal structures in the cells.
How are tissue samples obtained?
Most patients with cancer will have a biopsy. This may be done by removing a piece of the tumor during surgery, by fine needle aspiration, or with the use of an endoscope. The method depends on the type of mass and its 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. The sample is stained so that the pathologist can see any abnormal cell structures under a microscope.
The Pathology Report
Once a tissue sample is obtained, the pathologist will look for pre-cancerous or cancerous cells. The pathologist then writes a pathology report summarizing the findings. Your 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. You may also find it 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. 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 (the diagnosis made on the basis of the pathology report).
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.