Pathology can be defined as the science of the causes and effects of diseases.
A pathologist is a physician with special training that allows him or her to determine what kind of disease a patient may have, often by examination of tissues, organs, bodies, and bodily fluids.
In order to find out more about the tumor and determine the best treatment for the patient, doctors order diagnostic tests for the patient. The specific diagnostic test chosen for the patient is based on factors such as age, health level, previous test results, suspected tumor type, and symptoms.
A doctor will perform a physical examination to keep track of your level of health and how treatment may be affecting with you as well as how you are coping with the treatment's possible side effects. A doctor should perform an exam to look for liver enlargement, a possible sign GIST has invaded your liver, as well as any indication of fluid in the abdomen, possibly indicating involvement of the lining of the gut.
In order to check that organs are working properly, stool, urine and blood can be tested. Blood in the stool or sugar, protein or other abnormalities in the urine may indicate a problem. A blood test alone cannot verify or deny the existence of a GIST. However, bleeding from the tumor may cause some patients to become anemic. In order to determine if you have a low red blood cell count, a doctor can take blood samples from a vein.
In order to make a definite diagnosis, a biopsy is necessary. During a biopsy, the doctor removes a small sample of tissue from a mass in order to study it under a microscope and look for cancer cells. The doctor may acquire the sample via a needle guided by an imaging scan like an ultrasound or CT scan. A biopsy can be taken during other procedures involving the GI tract as well.
After acquiring the sample, the tumor cells are examined for appearance, shape, and features. This is known as the cells' morphology and histology. After this examination, the pathologist selects the proper immunohistological tests and applies them to the tumor samples. These tests expose the tissue sample to applied antibodies to find if the tumor cells express certain proteins. Information about proteins that are present or absent in the tumor may help the doctor to make a definitive diagnosis.
In addition to biopsies, there are several different types of imaging tests that a doctor can perform in order to help determine a diagnosis:
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Also known as an MRI, this scan creates a detailed picture of the inside of the human body via magnet and radio wave emission. The body absorbs radio waves which are then released in a certain form based on the type of tissue scanned or what diseases may be present. A computer then transforms this information into images that show concurrent sections of the body. MRIs are used mostly when recurrence or metastasis of a GIST is a concern. They are also frequently used when patients have GISTs arising in the rectum, as they delineate the local anatomy and potential tumor involvement particularly well in that area.
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This type of scan, also known as a CT Scan, creates detailed pictures of your organs using X-rays. This is useful for measuring the location, amount and mass of tumors in the body. These scans are considered to be the main test to reveal the presence of GIST and to find out what stage the cancer is at.
In order to produce a clearer picture when conducting x-rays, the lining of the stomach, colon, esophagus, and intestines are occasionally coated in a barium solution.
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Known informally as a PET scan, this type of test can be used to find out if a tumor has spread from the original location to other parts of the body, as well as state how metabolically active the tumor is. To perform the test, the doctor injects glucose (or other substances) that has been made radioactive into the patient's body. The area of potential spread is then photographed with the PET scanner. Cancer cells will usually appear brighter than surrounding tissue in the photograph. This is due to the cancer cells absorbing more radioactive glucose than regular cells.
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For this procedure, a small camera at the end of a bendable lighted tube is passed through the mouth, through the stomach and into the small bowel. The instrument, known as an endoscope, can detect masses and can remove small pieces of tissue from abnormal areas to be tested under a microscope. A variation of the endoscope with an ultrasound device at the end can be used to find exactly how deeply the GIST invades and to measure its size. Endoscopy can also be used from the other end, to look at the large bowel.
After finishing every necessary test, your doctor gathers the findings into a report for other doctors to evaluate. It may be a good idea to ask for a copy of this report, as it can help you more fully understand your cancer and help you in your own comprehension of the disease.
A list of your information. This includes your name, address, gender, and what day the procedure was taken on.
What part of the body the biopsy was taken and what procedure was used to take it.
In addition to the patient's personal medical history, this section contains what the doctor's thought is concerning the cause of symptoms or abnormal test results. Sometimes multiple possibilities may be listed, if the doctor is not sure of the precise cause.
The doctor looks at the sample without magnification, noting shape, weight, color and size.
A description of how the cells of a tissue sample look under microscopic magnification. The doctor includes an estimate of the stage of cancer in this section.
Not all GISTs share the same cell morphology. This means they do not all look alike. Roughly seventy percent of GISTs are made of spindle cells. These cells are long and skinny in appearance. Another twenty percent of GISTs are made of epithelioid cells. These cells are round or polygonal. The last ten percent of GISTs are a mix of the two cell types.
IHC testing for KIT, using an antibody to a substance on the surface of GIST cells (CD117) is another method for identifying GIST. Mutation in a gene called KIT causes 50 to 80% of GIST tumors. KIT, the product of the gene, is a protein on the surface of normal cells. Its job is to tell cells to grow and divide by sending signals. This signaling normally only happens when more cells are needed. When the KIT protein is irregular and fails to deactivate, GIST can occur. The malfunctioning KIT protein causes cells to grow, divide, and/or spread more aggressively. This uncontrolled growth eventually becomes a GIST. GIST is a member of a group of cancers called soft tissue sarcomas. Sarcoma is a term for a cancerous tumor that arises from connective tissue.
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The pathologist might offer information on how quickly the tumor cells are growing and replicating. When this activity occurs at high rates the tumor is growing more quickly and is predicted to grow if it is not taken out and to recur if it is removed. Mitotic count is a tally of the tumor cells that are in the middle of cell division or mitosis. Doctors use a ratio to describe the results, like 3/10HPF (for every ten high power fields under the microscope or "HPF", 3 cells are undergoing mitosis) or 10/50HPF (10 dividing cells seen in 50 microscopic fields are dividing). The higher the count of dividing cells, the more rapid the tumor's growth likely is. More recently, pathologists have tried to standardize their reporting to account for the fact that today’s modern microscopes have a higher power of magnification than in the past. Today, most pathologists will report will report mitoses/5 mm2 rather than per 50 HPF.
In some situations, testing the tumor for KIT or other mutations can provide your treating oncologist with critical information on the best drug (or doses) to be used. This procedure is done by preparing tumor DNA from a biopsy or surgery specimen. The testing can be done on tumors removed (or biopsied) up to 10 or more years. This test typically has to be special ordered by your physician and does not appear on the initial pathology report. If the testing is done, the pathology report would list which types of mutations were tested for (e.g. KIT and PDGFRA) and the result of the mutation (e.g. “tumor has a KIT exon 11 deletion of codons 557-558”). Most pathology departments would need to send the tumor to an outside laboratory, so this result would usually appear as a supplemental report. Even at hospitals that perform this testing, the result usually takes an additional 1-4 weeks and therefore would not be part of the initial pathology report.
The final diagnosis appears here, describing the results of all the tests and putting all the information together.
At the end, your pathologist will sign his name here.
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