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A small kidney tumor is a growth in the kidney that measures 4 cm (approximately 1.6 inches) or smaller, roughly the size of 2 nickels.
The kidneys are 2 bean-shaped organs roughly the size of a fist. The kidneys filter the blood and remove toxins and extra fluid from the body by making urine. The kidneys also make red blood cells, control blood pressure, and maintain bone health.
Most people do not feel any pain or other symptoms from a small tumor in the kidney, even when the tumor is cancerous. Most of the time, these tumors are discovered when people have medical imaging such as a computed tomography scan or ultrasound performed for an unrelated reason.
There are 2 major types of small kidney tumors, benign and malignant. Malignant tumors are cancers and have the ability to spread to other parts of the body. Although most kidney tumors are malignant and therefore cancerous, up to 20% are benign. Benign tumors do not spread to other parts of the body. Having no signs of spreading is important for deciding what treatments might be best for the tumor. The biggest risk factor for having a malignant small kidney tumor is age. Most renal cancers are diagnosed in people in their 60s. Other risk factors are smoking and certain genetic diseases.
There is no way to know for certain if a small kidney tumor is cancerous without removing the entire tumor. Because benign kidney tumors do not require removal, a kidney specialist known as a urologist may order additional tests to help determine if a tumor is benign before treatment decisions are made. These tests may include imaging tests or a biopsy, in which a sample of the tumor is taken with a needle. These tests may help avoid unnecessary procedures.
Even if a small kidney tumor is cancerous, it is unlikely to rapidly grow or spread to other parts of the body. The risk of spreading is mostly based on size. If cancer is discovered and treated in a small kidney tumor, it is has little chance of spreading. In addition, most small kidney cancers will not spread or cause death if left alone and watched for growth. The amount of growth helps decide whether treatment is needed.
There are several options for treating a small kidney tumor that is possibly cancerous. For some people, surgical treatment is the preferred option. Surgical treatment options include removing the entire kidney (radical nephrectomy) or removing the portion of the kidney containing the tumor (partial nephrectomy). Another treatment option is using a needle placed through the skin to either freeze or heat the tumor (percutaneous ablation).
For other patients, simply observing the tumor, also known as watchful waiting or active surveillance, may be the best option, particularly when a person is too elderly or ill to gain any benefit from treating the tumor. A urologist should counsel patients with small kidney tumors about treatment options for each individual’s unique situation.
American Cancer Societywww.cancer.org/cancer/kidney-cancer/treating/by-stage.html
Conflict of Interest Disclosures: Dr Kang reported receipt of royalties from Wolters Kluwer. Dr Bjurlin reported receipt of personal fees from Ultimate Medical Academy. Dr Huang reported membership on the American Society of Clinical Oncology Guidelines Panel for Small Renal Masses.
Source: Kang SK, Bjurlin MA, Huang WC. Management of small kidney tumors in 2019. JAMA. 2019;321(16):1622-1623. doi:10.1001/jama.2019.1672
Kang SK, Bjurlin MA, Huang WC. Small Kidney Tumors. JAMA. 2019;322(6):588. doi:10.1001/jama.2019.8509
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