Renal Oncocytoma

What is renal oncocytoma?

Renal oncocytoma is a noncancerous (benign) growth in one or both of your kidneys. These lesions may not cause symptoms or need treatment. Healthcare providers often discover renal oncocytomas accidentally while performing diagnostic tests for another issue.

What does renal oncocytoma mean?

Renal oncocytoma (REE-null ahn-CAH-sy-TOE-muh) means:

• Renal: Latin word for kidney.
• Oncocytoma: Medical term for mass or tumor made of oncocytes.

How common is renal oncocytoma?

Up to 7% of kidney growths are renal oncocytomas. As many as 13% of people with renal oncocytoma have multiple growths in both kidneys, a condition known as renal oncocytosis.

Who is at risk for renal oncocytomas?

Renal oncocytomas can affect all ages, races and genders. They’re more common in people assigned male at birth (AMAB) and in those over 60 years old.

Renal oncocytoma can also occur in genetic conditions like Birt-Hogg-Dubé syndrome. This genetic condition causes an increased risk of kidney cysts, benign growths like renal oncocytoma and kidney cancer.

Can renal oncocytomas become malignant (cancerous)?

Renal oncocytomas are unlikely to become cancerous. However, studies have found rare instances where people with renal oncocytomas with no known history of cancer develop metastatic cancer in their liver or bones. This indicates that their oncocytoma became cancerous.

What’s the difference between renal oncocytoma and renal cell carcinoma?

Renal oncocytomas share a similar appearance on non-invasive imaging to renal cell carcinomas, which is the most common type of kidney cancer.

Unfortunately, imaging tests can’t show whether a tumor is benign or malignant. Healthcare providers may recommend surgery to remove the mass. A biopsy can confirm a diagnosis of renal oncocytoma or kidney cancer.

What’s the difference between cysts and tumors?

Cysts and tumors share similarities and differences:

• Cysts are small sacs that may contain fluid, air or solid material. Most cysts aren’t cancerous.
• Tumors are solid masses of tissue. A tumor may or may not be cancerous.

What causes renal oncocytoma?

Most kidney cysts like renal oncocytomas have no known cause. Some experts believe that genetic changes (mutations) that occur after birth make some people more prone to these cysts.

Are renal oncocytomas inherited?

Some families have an inherited gene change or mutation that increases their risk for developing multiple renal oncocytomas in both kidneys. Conditions such as tuberous sclerosis complex and Birt-Hogg-Dubé syndrome cause growths to form in organs.

What are renal oncocytoma symptoms?

An estimated 3 in 4 people with renal oncocytomas don’t have symptoms. When symptoms occur, they can be a lot like kidney cancer symptoms, such as:

• Blood in your urine (hematuria).
• Flank pain.
• A lump you can feel on the side of your affected kidney.

How is renal oncocytoma diagnosed?

Healthcare providers often discover renal oncocytomas when reviewing imaging tests like kidney ultrasounds, MRIs or CT scans to check for other problems, such as kidney stones.

Renal oncocytomas and cancerous tumors like renal cell carcinoma look alike on imaging scans. This makes it difficult for healthcare providers to determine whether a person has a noncancerous cyst or a cancerous tumor. A biopsy to test the tumor cells is the only way to make an accurate diagnosis. This biopsy takes place after surgery to remove the mass.

Up to 45% of biopsied kidney tumors aren’t cancerous. For this reason, your healthcare provider may recommend watching the tumor (active surveillance) instead of surgery, especially if the tumor is small and doesn’t cause problems. During active surveillance, you undergo regular imaging scans to monitor the tumor for growth or changes that could indicate cancer.

Do benign kidney tumors need to be removed?

Renal oncocytomas that don’t grow or cause problems may not need treatment. Your healthcare provider may recommend surgery if the diagnosis is uncertain or you have symptoms.

Surgery may remove only the mass (partial nephrectomy) or the entire kidney (radical nephrectomy). If you have a kidney removed, you can still live an active life with one kidney.

What is the prognosis for someone with renal oncocytomas?

Benign renal oncocytomas don’t affect your ability to lead a full, active life. It’s extremely rare for oncocytomas to become cancerous. Surgically removed oncocytomas don’t tend to come back. The outlook may be different if you have a genetic condition that causes tumors to form in your organs.

When should I call my doctor?

Call your healthcare provider if you experience:

• Blood in your urine.
• A lump or pain in your side that doesn’t go away.
• Unexplained fever or weight loss.

What should I ask my provider?

You may want to ask your healthcare provider:

• What caused the renal oncocytoma?
• Do I need surgery?
• Am I at risk for cancer?
• Should I look out for signs of complications?

What’s the difference between renal oncocytoma and chromophobe renal cell carcinoma?

Chromophobe renal cell carcinoma is a rare kidney cancer. It develops in the small tubes (tubules) that help your kidneys remove waste from your blood. Your urinary system gets rid of this waste. About 5% of kidney cancers are the chromophobe type.

People with Birt-Hogg-Dubé syndrome are more likely to develop kidney tumors. They have a higher risk of both noncancerous tumors (renal oncocytomas) and cancerous tumors (chromophobe renal cell carcinoma). Surgery and a tumor biopsy can determine the tumor type.

A note from Cleveland Clinic

Renal oncocytomas are noncancerous kidney cysts that rarely cause symptoms. Healthcare providers often find the cyst after testing for another condition. Because these cysts share similarities with renal cell carcinoma (a kidney cancer), you may need surgery to remove the mass. A biopsy can confirm whether you have renal oncocytoma or kidney cancer.