Overview
Primary kidney or renal cancer is a malignant tumor that originates in the kidney. There are two main types of primary kidney cancer in adults, renal cell carcinoma (also called renal cell adenocarcinoma) and transitional cell carcinoma. Wilms' tumor is the most common type of kidney cancer in children but is not discussed here. It is also possible that other types of cancers may travel to the kidneys from distant parts of the body (metastasize to the kidney). These are called secondary kidney tumors and may include sarcomas, lymphomas, and other malignancies.
Approximately 85 percent of all kidney cancers are renal cell carcinomas. The Kidney Cancer Profiler pertains to renal cell carcinoma only. Transitional cell carcinoma is discussed on this website, in the Bladder Cancer Center. To find out more information on Wilms' tumor or transitional cell carcinoma, contact the American Cancer Society or The National Wilms' Tumor Study Group, or consult your physician.
Renal cell carcinoma begins deep within the kidney in a section of the kidney called the proximal renal tubule. This is a very small part of the kidney that is responsible for filtering the blood and helping in the formation of urine.
As the cells become cancerous, they begin to grow in an uncontrolled fashion, creating a tumor. The tumor can then grow and spread (metastasize) to other, distant organs. Renal cell carcinoma tends to grow out of the kidney into the nearby blood vessels, making surgical removal extremely difficult. It frequently metastasizes early and does not have to grow extremely large before it can spread to distant sites.
Unlike other cancers, renal cell carcinomas occasionally shrink partially or completely without treatment. This is called regression of the tumor, and occurs in less than 1 percent of cases. This trait is thought to be due to the activity of the immune system of the patient as it tries to fight the tumor. This observation has led to speculation that the immune system is capable of causing complete elimination of renal cell carcinoma, although this has not been shown to be effective treatment. Also, the regression is generally short and the tumor grows back.
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Tumor Types
Once renal cell carcinoma is diagnosed, the tumor cells are studied under the microscope to determine the cell type (also called histology). This is because certain cell types are more common or more aggressive in their behavior than others, and knowing the cell type will help determine treatment planning. The names of the cell types come from the description of the cell's appearance and other characteristics and include: clear cell, granular cell, papillary and sarcomatoid. Clear cell is the most common type of renal cell carcinoma and sarcomatoid is the most aggressive type. It grows and metastasizes quickly, and has a poor prognosis.
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Symptoms
Detecting renal cell carcinoma in its early stages is difficult because symptoms typically do not occur until the tumor has grown fairly large. At that point, it displaces other nearby organs, causing symptoms. One-third of all patients show evidence that the tumor has spread (metastasized) at the time of diagnosis. Many kidney (renal) tumors are found incidentally on x-rays or ultrasound examinations performed for reasons that don't relate to the tumor or any of its potential symptoms.
The most common symptom related to the tumor itself is blood in the urine, although this occurs in only 40 percent to 50 percent of patients. There may be pain or pressure on the side of the back near the lower portion of the rib cage where the kidney and tumor are located. There may be a thickening or bulging that can be seen or felt as the tumor grows. If the tumor has spread to distant organs, symptoms may vary, depending on the specific organ affected, though patients may notice unexplained weight loss, fevers, anemia, or high blood pressure.
In the case of many cancers, including renal cell carcinoma, paraneoplastic syndromes may occur. These are a distinct group of symptoms that may be mild or severe. In some cases, they may be life threatening.
Signs or symptoms of a paraneoplastic syndrome are variable but can include weight loss, high blood pressure (hypertension), anemia, abnormal liver function, high calcium levels in the blood with or without symptoms, and increased numbers of red blood cells. Some patients with renal cell carcinoma develop symptoms of a paraneoplastic syndrome before they show symptoms directly related to the tumor.
Although they are known to be associated with cancer, paraneoplastic syndromes are poorly understood. They do not occur because of metastasis or direct invasion of the tumor, and the symptoms often mimic those resulting from other diseases. The symptoms seem unrelated to the tumor itself and can be temporarily controlled, although definitive treatment of the paraneoplastic syndrome requires direct treatment of the tumor.
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Treatment
The type of treatment selected will depend upon tumor grade and stage as well as your general health. Multiple types of treatment are commonly used for kidney cancer: surgery, radical nephrectomy, nephrectomy with thrombectomy, partial nephrectomy, nephrectomy to control symptoms, surgery to resect a distant metastasis, adjuvant therapy, radiation therapy, chemotherapy, and immunotherapy.
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