Renal, or kidney, cancer is more common in people older than 40, according to the National Cancer Institute. The institute says that almost twice as many men than women have the disease. The cause of kidney cancer is unknown, but people who smoke, have high blood pressure or are overweight are more likely to develop it. Symptoms including blood in the urine and a lump in the abdominal area may indicate the presence of cancer cells in the kidney, and should be examined by a medical professional. There are several possible types of renal cancer. The most common is renal cell carcinoma.
Renal Cell Carcinoma
The American Cancer Society says that 90 percent of kidney cancers are renal cell carcinomas. This type of cancer often appears as a single tumor in the kidney and is typically found before cancer cells have traveled to other organs. Renal cell cancers vary in shape, color and size. The most common type of renal cell cancer is made up of very pale-colored cells. Other types of renal cell carcinomas include papillary, chromophobe and collecting duct. Cancer cells that don't fit into one of these categories are called unclassified renal cell carcinomas. Rarely are renal carcinomas unclassified.
Transitional Cell Carcinoma
Some patients have a type of renal cancer called transitional cell carcinoma, or urothelial carcinoma. This type of cancer occurs at the junction of the kidney and ureter, which carries urine from the kidney to the bladder. In fact, transitional cell carcinomas look similar to bladder cancer cells. The American Cancer Society says this type of kidney cancer is diagnosed in up to 10 percent of cases.
Rare Renal Cancer Types
Renal sarcoma is a type of kidney cancer that accounts for 1 percent of cases, according to the American Cancer Society. In contrast to cells, where carcinomas form, sarcomas develop in tissues. In the case of renal sarcoma, the cancer develops in the connective tissues of the kidney.
Although most kidney cancers are diagnosed in adults, a type of kidney cancer called Wilms tumor is more common in children. The National Cancer Institute says most cases appear in children younger than 5.
