A pathology report is a document that describes a patient's diagnosis and tumor features based on naked-eye (gross) and microscopic examination of tissue samples by a pathologist. These tissue samples may be obtained by biopsy and/or surgery.
For kidney cancer, imaging tests, such as CT scan and/or MRI, may show enough detail to diagnose the tumor type. However, if imaging tests are inconclusive, the doctor may perform a biopsy to confirm the diagnosis. A biopsy is the removal of a small amount of tissue from the kidney. This can be done either with a small needle that extracts cells from the tissue and is called a Fine Needle Aspiration (FNA) biopsy; or it may be done using a needle core biopsy gun, where the needle cuts a thin core (sliver) of tissue. This biopsy specimen is examined under a microscope by a pathologist, who determines whether the tumor is benign or malignant, as well as specific features of the patient's disease.
In some situations, your doctor may not biopsy the tumor and may proceed to surgery based on the imaging report. After a diagnosis is made, the doctor may perform surgery to remove either all or part of the kidney where the tumor is located (radical or partial nephrectomy). The surgeon may also remove nearby tissues and lymph nodes as part of these procedures. Further pathologic analysis will be conducted to determine additional features of the disease, such as the tumor type, the extent of invasion and lymph node involvement. All information obtained from the biopsy and surgical specimens will be included in the pathology report, which you may obtain from your doctor’s office.
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A pathology report is written in medical language and the technical wording on it can sometimes be confusing. This guide will help you better understand the report and your diagnosis. A typical pathology report may include the following:
Also called the “gross” description, this section of the report describes what the tissue looks like to the naked eye. The pathologist (or their assistant) will dissect the kidney to closely examine the entire tissue. The "gross" description describes the physical characteristics of the specimen, including the size, weight, location within the kidney, color of the tissue, the extent of the tumor and it's relationship to the margins. This macroscopic examination helps the pathologist determine what parts of the tissue to look at under a microscope. The gross examination also provides information to help your doctor “stage” your tumor, such as the tumor size and whether the tumor extends out of the kidney and into adjacent tissue.
The microscopic evaluation describes the appearance of the tumor cells under a microscope. From a biopsy sample, the pathologist can determine the cell type (histologic subtype) of the tumor and the tumor grade. From a surgical specimen, the pathologist can also determine the cell type and tumor grade, as well as margin status, extent of invasion, and lymph node involvement. Extent of invasion and lymph node involvement may be assessed radiographically as well.
There are several types of kidney cancer, which look different under the microscope and also have different genetic abnormalities. The most common subtypes of kidney cancer are described below (this list is not inclusive):
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Clear cell is the most common type of renal cell carcinoma and makes up about 70% to 80% of all cases. These cells appear pale or clear under a microscope.
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Papillary is the second most common type of renal cell carcinoma and makes up about 10% of all cases. These tumors generally form finger-like projections called papillae. There are two types of papillary renal cell carcinoma:
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Chromophobe renal cell carcinoma constitutes about 5% of all renal cell carcinomas. This subtype of renal cell carcinoma tends to be very indolent and rarely spreads. When they do spread, which may be ten to fifteen years later, they are difficult to treat, but they rarely metastasize even when they become very large tumors.
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These are rare (less than 1%) forms of renal cell carcinoma in which the cells form irregular tubules. Renal Medullary Carcinoma primarily occurs in young adults with sickle cell trait. Both of these tumors are aggressive, and do not respond well to conventional treatments.
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Makes up 3% to 5% of all renal cell carcinomas. These tumors look different than any other subtype and may be a combination of subtypes. Unclassified renal cell carcinomas are usually very aggressive.
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About 5% to 10% of kidney cancers are urothelial carcinomas, which start in the cells lining the renal pelvis. These cells are the same type of cell found in the ureters and urinary bladder. This means urothelial tumors behave more like urinary bladder tumors than renal cell carcinomas.
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An oncocytoma is a benign kidney tumor. Oncocytomas can grow large, but usually do not invade nearby tissue or spread to other parts of the body.
The pathologist may then assign a grade to the tumor using the Fuhrman Nuclear Grading System which looks at cells’ nuclei (the part of the cell that contains DNA and controls growth) and the nucleoli (small granules in the nucleus that store proteins). This system is only applicable to those with clear cell renal cell carcinoma, as it has not been adequately validated with the other renal cell carcinoma types.
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Nuclei appear small, dark, round and uniform and do not have easily visible nucleoli.
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Nuclei are larger and have a small nucleolus, which is only visible at higher magnification (400x).
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Nuclei are larger than grade 2, may be more irregular than normal, and have prominent nucleoli that are visible at a lower magnification (100x).
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Nuclei appear most irregular with the most prominent nucleoli.
In patients that have a definitive surgical resection (partial or radical nephrectomy), the doctor will remove the tumor as well as a margin of healthy tissue around it. The pathologist will examine the margin and may measure the distance from the cancer to the outer edges of the tissue.
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If tumor cells are present at the edge of the tissue, the margins are considered “positive” or “involved”.
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If cells are not present at the edge of the tissue, the margins are considered “negative,” “clear,” or “not involved”.
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The pathologist will include information on the extent of tumor invasion beyond the kidney in the pathology report. For example, the pathology report will tell you whether the cancer is confined to the kidney or invasive into the perinephric fat, the renal sinus, the renal vein, the inferior vena cava, adrenal gland or beyond Gerota’s fascia or some combination of the above.
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The pathologist will also look closely at the small caliber blood and lymph vessels around the tumor to determine if any cancer cells have invaded them. When cancer cells invade these vessels, it is called a lymphovascular invasion.
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The lymph nodes are responsible for filtering waste products from the lymphatic fluid before it circulates back to the rest of the body. If your lymph nodes contain cancer cells, there is a high risk the cancer could spread to the rest of your body. Your pathology report will contain information about the status of your lymph nodes if they were removed at the time of surgery.
This is where your pathologist will write the final diagnosis. After thoroughly examining the tumor, kidney and surrounding tissue, this summary should include the type of tumor, tumor grade and tumor extent, which will determine the pathologic stage of your cancer. The pathologic stage data will be combined with other diagnostic tests to determine the overall stage of the kidney cancer.
If you find that your pathology report is still puzzling, or have further specific questions regarding your diagnosis, talk to your doctor.
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