Lesions on the kidney can be caused by cancer, but they can also be benign cysts, reports Mayo Clinic. There is no known cause for cysts, although they are a common type of kidney lesion.
Most solid kidney tumors are caused by cancer, notes the Urology Care Foundation. Doctors usually do not even biopsy solid lesions before removing them, because of the risk of false negatives and because of how rarely they are caused by anything else. Although cancer can develop in anyone, there are known risk factors for kidney cancer. These include smoking cigarettes, a diet high in fried foods, obesity and a family history of kidney cancer. Certain other conditions, including Von Hippel-Lindau syndrome, hypertension and tuberous sclerosis, may also increase the risk.
Clear lesions are usually kidney cysts and are typically harmless, reports Mayo Clinic. They can be caused by other diseases, but they sometimes form for no apparent reason. These cysts rarely have any symptoms and usually do not need treatment. However, they can sometimes develop complications, such as becoming infected or bursting. Some can also grow or be located in a place where they block urine from passing normally through the kidney, which can lead to serious health problems. These cysts can be treated by surgical removal or by having the doctor puncture and drain the cyst.