According to the American Cancer Society, over 50,000 people in the United States were estimated to have been diagnosed with kidney cancer in 2007; and over 12,000 people will die from this disease. The majority of patients diagnosed with kidney cancer are over the age of 45 with the highest incidences between the ages of 55 and 84.
Unfortunately, kidney cancer is often diagnosed at a late stage because the tumors can become quite large without causing any symptoms or pain and because the kidneys are located deep inside the body and there is no means of seeing or feeling small tumors on the kidneys during a physical exam.
It is important to understand that with timely diagnosis and treatment, kidney cancer can be cured. If found early, the survival rate for patients with kidney cancer ranges from 79 to 100 percent. There are over 100,000 survivors of kidney cancer alive in the United States today. The following information addresses the most common types of kidney cancer and is meant to serves as a supplement to the discussions you have with your physician.
Renal Cell Carcinoma (RCC)
Renal Cell Carcinoma (RCC) is the most common type of kidney cancer, accounting for approximately 85 percent of all malignant kidney tumors. In RCC, cancerous (malignant) cells develop in the lining of the kidney tubules and grow into a mass called a tumor. Like many other cancers, the growth begins small and grows larger over time. RCC typically grows as a single mass. However, there are cases where a kidney may contain more than one tumor, or tumors are found in both kidneys at the same time.
There are five main types of renal cell carcinoma that are identified by examining the tumor under a microscope:
- Clear Cell RCC: Clear Cell RCC is the most common form of renal cell carcinoma, accounting for about 80 percent of people with kidney cancer. When viewed under a microscope, the individual cells that make up clear cell renal cell carcinoma appear very pale or clear.
- Papillary RCC: Papillary RCC is the second most common type. About 10 to 15 percent of people have this form. These cancers form little finger-like projections (called papillae).
- Chromophobe RCC: The third most common form of renal carcinoma is chromophobe RCC, accounting for about 5 percent of cases. Like clear cell carcinoma, the cells of these cancers are also pale, but are much larger and have certain other distinctive features.
- Collecting Duct RCC: The rarest form of RCC is collecting duct renal carcinoma. The major characteristic of collecting duct RCC is that the cancer cells can form irregular tubes.
- Unclassified RCC: About 5 percent of renal cancers are unclassified because their appearance does not fit into any of the other categories.
Other Types of Cancerous Kidney Tumors
Less common kidney cancer types than renal cell carcinoma include transitional cell carcinomas, Wilms tumors and renal sarcomas.
Transitional Cell Carcinoma
About 5 to 10 percent of all kidney tumors are transitional cell carcinomas, also known as urothelial carcinomas. Transitional cell carcinomas begin in the renal pelvis (the junction of ureter and kidney). Under the microscope, transitional cell carcinomas look like bladder cancer cells and act very much like bladder cancer. Studies have shown that, like bladder cancer, these cancers are linked to cigarette smoking and occupational exposures to certain cancer-causing chemicals.
About 90 percent of transitional cell carcinomas of the kidney are curable if they are found early enough. The chances for cure drop dramatically if the tumor has grown into the ureter wall, or if it has a more aggressive (high-grade) appearance when viewed under the microscope.
About 5 to 6 percent of all kidney cancers are Wilms tumors. This type of cancer is almost always found in children and is extremely rare among adults.
Renal sarcomas are a rare type of kidney cancer (less than 1 percent of all kidney tumors) that begins within the kidney's connective tissue.
Benign (Non-Cancerous) Kidney Tumors
Some types of kidney tumors (including renal cell adenomas, renal oncocytomas and angiomyolipomas) do not usually spread (metastasize) to other parts of the body, although they can still grow and cause problems.