Renal cancer is cancer that starts in the kidney. It accounts for roughly 3% to 5% of all adult cancers, is about twice as common in men as in women, and is typically diagnosed around age 65. The most common form, renal cell carcinoma (RCC), makes up the vast majority of cases. Because kidney cancer rarely causes symptoms in its early stages, many tumors are found by accident during imaging for an unrelated health issue.
Types of Renal Cell Carcinoma
Not all kidney cancers behave the same way. Clear cell RCC is by far the most common subtype, representing 70% to 80% of all cases. It gets its name from the way the cancer cells look under a microscope: pale or “clear.” Clear cell tumors tend to respond differently to treatment than other subtypes, which is why pathologists distinguish between them.
Papillary RCC is the second most common subtype. Beyond that, there are several rarer forms, including chromophobe, collecting duct, and medullary RCC. Each has a distinct biology, and the subtype can influence both prognosis and treatment choices.
Symptoms and Early Warning Signs
Kidney cancer is often called a “silent” disease because it produces no clear symptoms early on. Many people feel perfectly fine until the tumor has grown large enough to press on surrounding structures or until it shows up on a scan done for another reason entirely.
When symptoms do develop, the most common include:
- Blood in the urine, which can look pink, red, or cola-colored
- Persistent back or side pain that doesn’t go away
- Unexplained weight loss
- Loss of appetite
- Ongoing fatigue
None of these symptoms is unique to kidney cancer, and many people with these complaints will turn out to have something far less serious. Still, blood in the urine or unexplained flank pain that lingers warrants investigation.
Risk Factors
Three well-established, modifiable risk factors stand out: smoking, obesity, and high blood pressure. Cigarette smoking is linked to both higher incidence and higher death rates from kidney cancer, though the exact biological pathway is still being studied. Obesity raises the risk as well, likely through hormonal and metabolic changes that promote cell growth. Interestingly, researchers have observed an “obesity paradox” in which obese patients who do develop kidney cancer sometimes have better survival outcomes than leaner patients, a finding that remains poorly understood.
High blood pressure, whether from lifestyle factors or genetics, is independently associated with kidney cancer risk. Beyond these three, older age, male sex, and certain inherited genetic conditions also increase susceptibility.
Hereditary Kidney Cancer Syndromes
A small percentage of kidney cancers run in families. The best-known hereditary condition is Von Hippel-Lindau (VHL) syndrome, caused by a mutation in a gene that normally acts as a brake on cell growth. Everyone inherits two copies of the VHL gene. People with VHL syndrome are born with one faulty copy. When the second copy picks up a mutation during their lifetime, cells in the kidney (and other organs) lose the ability to regulate their growth, allowing tumors and cysts to form. Almost everyone who inherits the first VHL mutation will eventually develop features of the syndrome.
Other hereditary syndromes linked to kidney cancer exist as well, including Birt-Hogg-Dubé syndrome. If multiple family members have been diagnosed with kidney cancer, or if kidney cancer appears at an unusually young age, genetic counseling can help determine whether a hereditary condition is involved.
How Kidney Cancer Is Diagnosed
Most kidney tumors are discovered incidentally, during an abdominal ultrasound or CT scan ordered for something else. Once a suspicious mass is found, a multi-phase contrast-enhanced CT scan of the abdomen and chest is the standard next step. This imaging captures the mass at different moments as contrast dye flows through the kidney, helping doctors determine whether the mass is solid, how large it is, and whether it has spread.
If the CT results are unclear, an MRI or contrast-enhanced ultrasound can provide additional detail, particularly for small masses or when doctors need to assess whether the tumor extends into nearby blood vessels. A biopsy, where a small tissue sample is taken with a needle, is not always needed. When imaging clearly shows a contrast-enhancing solid mass and surgery is planned, doctors typically proceed without a biopsy. Biopsies are more commonly performed when the mass is small and the patient is considering surveillance rather than immediate surgery, or before non-surgical treatments like tumor ablation.
Stages of Kidney Cancer
Staging describes how large the tumor is and how far it has spread. It directly shapes treatment decisions and gives a general picture of outlook.
- Stage I: The tumor is 7 cm or smaller (roughly the size of a tennis ball) and is entirely contained within the kidney. Stage I is further divided into T1a (4 cm or smaller) and T1b (between 4 cm and 7 cm).
- Stage II: The tumor is larger than 7 cm but still confined to the kidney. T2a covers tumors up to 10 cm; T2b covers those above 10 cm.
- Stage III: The tumor has grown into major veins near the kidney or into the fatty tissue surrounding the kidney, or it has reached nearby lymph nodes, but it hasn’t spread to distant organs.
- Stage IV: The tumor has invaded beyond the fibrous capsule surrounding the kidney, has spread into the adrenal gland sitting on top of the kidney, or has metastasized to distant sites like the lungs, bones, or brain.
Treatment Options
Surgery remains the primary treatment for kidney cancer that hasn’t spread widely. The two main surgical approaches are partial nephrectomy, which removes only the tumor and a small margin of healthy tissue, and radical nephrectomy, which removes the entire kidney along with surrounding tissue.
Current guidelines favor partial nephrectomy whenever it’s technically feasible, regardless of tumor size. For tumors 4 cm or smaller (T1a), partial removal is the strong recommendation. For tumors between 4 cm and 7 cm (T1b), partial nephrectomy is still preferred over removing the whole kidney. The goal is to preserve as much healthy kidney tissue as possible, which protects long-term kidney function and reduces the risk of future cardiovascular problems linked to reduced kidney capacity.
For larger or more complex tumors, or when the tumor has grown into nearby veins, radical nephrectomy may be the safer option. In cases where the cancer has spread to distant organs, systemic treatments like immunotherapy or targeted therapy drugs that block the blood supply tumors need to grow are used, sometimes in combination with surgery.
For very small, slow-growing tumors, particularly in older patients or those with other serious health conditions, active surveillance is an option. This means monitoring the tumor with regular imaging rather than treating it immediately, with the plan to intervene if it shows signs of growth.
Survival Rates by Stage
Five-year relative survival rates, based on data from people diagnosed between 2015 and 2021, paint a clear picture of how much stage matters:
- Localized (confined to the kidney): 93%
- Regional (spread to nearby lymph nodes or tissues): 76%
- Distant (metastasized to other organs): 19%
These numbers reflect averages across all patients and all subtypes. Individual outcomes vary based on the specific type of RCC, overall health, age, and how well the cancer responds to treatment. The high survival rate for localized disease underscores why incidental early detection, even when it happens by chance during unrelated imaging, often turns out to be a significant stroke of luck.