Overview
Kidney cancer, also called renal cancer, is a disease in which kidney cells become malignant and grow out of control, forming a tumor. The kidneys are two bean-shaped organs, each about the size of a fist, located on either side of the spine in the lower abdomen. Their main function is to filter blood and produce urine.
Most kidney cancers first appear in the lining of tiny tubes (tubules) in the kidney. This type of kidney cancer is called renal cell carcinoma (RCC), which accounts for about 90% of kidney cancers. The good news is that most kidney cancers are found before they spread to distant organs, and cancers caught early are easier to treat successfully.
Kidney cancer is among the 10 most common cancers in both men and women. The average age at diagnosis is 64, and it's very uncommon in people younger than 45. Men are about twice as likely as women to develop kidney cancer. The overall 5-year survival rate for kidney cancer is about 75%, but this varies significantly based on the stage at diagnosis.
Symptoms
In the early stages, kidney cancer rarely causes signs or symptoms. As the tumor grows larger, symptoms may appear. It's important to note that these symptoms can also be caused by other, less serious conditions.
Blood in Urine (Hematuria)
The most common symptom, appearing in 40-50% of cases. Urine may appear pink, red, or cola-colored. The bleeding may be intermittent.
Kidney Mass or Lump
A mass or lump in the side or abdomen. Most kidney masses are found incidentally during imaging tests for other conditions.
Flank Pain
Persistent pain in the side or back, below the ribs and above the hip. This occurs in about 40% of patients.
Groin Mass
Swelling in the groin area may indicate spread to lymph nodes or a varicocele caused by tumor blockage.
Urinary Changes
Changes in urination patterns, including increased frequency, urgency, or difficulty urinating.
Systemic Symptoms
Fatigue, unexplained weight loss, fever, night sweats, and loss of appetite may occur as the cancer progresses.
Important: Many kidney tumors are found incidentally during imaging tests for other conditions. Regular check-ups and being aware of changes in your body are crucial for early detection.
Causes
The exact cause of kidney cancer is not known, but several factors can increase the risk of developing the disease. Kidney cancer occurs when kidney cells develop mutations in their DNA, causing cells to grow and divide rapidly.
Cellular Changes
Kidney cancer begins when cells in the kidney acquire mutations in their DNA. These mutations cause cells to grow and divide uncontrollably. The accumulating abnormal cells form a tumor that can extend beyond the kidney. Some cells can break off and spread (metastasize) to distant parts of the body.
Genetic Factors
Several inherited syndromes can increase the risk of kidney cancer:
- Von Hippel-Lindau (VHL) disease: A hereditary disorder that increases risk of several cancers
- Hereditary papillary renal cell carcinoma: Causes multiple papillary tumors
- Birt-Hogg-Dubé syndrome: Causes benign skin tumors and increases kidney cancer risk
- Hereditary leiomyomatosis: Associated with an aggressive form of kidney cancer
Environmental Factors
Exposure to certain substances and lifestyle factors may contribute to kidney cancer development, including workplace exposure to chemicals like cadmium, certain herbicides, and organic solvents.
Risk Factors
Factors that can increase the risk of kidney cancer include:
Modifiable Risk Factors
- Smoking: Doubles the risk of kidney cancer
- Obesity: Excess weight may cause hormonal changes that increase risk
- High blood pressure: Both hypertension and some medications used to treat it
- Workplace exposures: Cadmium, herbicides, and organic solvents
- Certain medications: Long-term use of some pain medications
Non-modifiable Risk Factors
- Age: Risk increases with age, most common in people 60 and older
- Gender: Men are twice as likely to develop kidney cancer
- Race: Slightly higher rates in African Americans and American Indians
- Family history: Having a sibling with kidney cancer increases risk
- Genetic syndromes: VHL disease, hereditary papillary RCC
- Kidney disease: Advanced kidney disease and dialysis treatment
Types of Kidney Cancer
Several types of cancer can develop in the kidneys. Understanding the type is important for determining treatment:
Renal Cell Carcinoma (RCC)
About 90% of kidney cancers are renal cell carcinomas. Main subtypes include:
- Clear cell RCC (70-75%): Most common type, cells appear clear or pale under microscope
- Papillary RCC (10-15%): Second most common, forms finger-like projections
- Chromophobe RCC (5%): Cells are pale like clear cell but larger
- Collecting duct RCC (1%): Rare and aggressive form
- Unclassified RCC: Doesn't fit into other categories
Other Kidney Cancers
- Transitional cell carcinoma (5-10%): Begins in the renal pelvis, similar to bladder cancer
- Wilms tumor: Almost always occurs in children
- Renal sarcoma: Rare, begins in blood vessels or connective tissue
Benign Kidney Tumors
Not all kidney tumors are cancerous. Benign tumors include:
- Renal adenoma
- Oncocytoma
- Angiomyolipoma
Diagnosis
Many kidney cancers are found incidentally during imaging tests for other conditions. When kidney cancer is suspected, several tests may be performed:
Physical Examination and History
- Complete medical history
- Physical exam to check for lumps or swelling
- Discussion of symptoms and risk factors
Laboratory Tests
- Urinalysis: Checks for blood and other substances in urine
- Complete blood count: May show anemia or other abnormalities
- Blood chemistry tests: Assess kidney function and other organs
- Liver function tests: Check if cancer has spread
Imaging Tests
- CT scan: Most common test, provides detailed cross-sectional images
- MRI: Useful for examining blood vessels and detecting spread
- Ultrasound: Can distinguish solid tumors from fluid-filled cysts
- Chest X-ray: Checks for lung metastases
- Bone scan: If bone metastases are suspected
- PET scan: May help determine cancer spread
Biopsy
Unlike many cancers, kidney cancer can often be diagnosed based on imaging alone. Biopsy may be performed when:
- Imaging results are unclear
- The tumor is small and monitoring is being considered
- Metastatic disease needs confirmation
- Treatment without surgery is planned
Staging
Staging describes the extent of cancer and helps determine treatment options. The TNM system is used:
TNM Classification
- T (Tumor): Size and extent of the main tumor
- N (Nodes): Spread to nearby lymph nodes
- M (Metastasis): Spread to other parts of the body
Stage Groupings
- Stage I
- Tumor ≤7 cm, confined to kidney, no lymph node involvement or metastases
- Stage II
- Tumor >7 cm, still confined to kidney, no lymph node involvement or metastases
- Stage III
- Tumor extends into major veins or invades adrenal gland or surrounding tissues, OR spreads to nearby lymph nodes
- Stage IV
- Cancer has spread beyond Gerota's fascia, OR to distant lymph nodes or organs
Prognostic Factors
Factors affecting prognosis include:
- Stage at diagnosis
- Tumor grade (how abnormal cells look)
- Patient's overall health
- Specific RCC subtype
- Presence of sarcomatoid features
Treatment Options
Treatment depends on the stage of cancer, overall health, and patient preferences. Options include:
Surgery
Surgery is the primary treatment for most kidney cancers:
- Radical nephrectomy: Removes entire kidney, adrenal gland, surrounding tissue, and sometimes lymph nodes
- Partial nephrectomy: Removes tumor and small margin of healthy tissue, preserving kidney function
- Laparoscopic or robotic surgery: Minimally invasive options with faster recovery
- Cryoablation or radiofrequency ablation: For small tumors in selected patients
Systemic Therapies
Treatment by Stage
- Stage I-II: Surgery (partial or radical nephrectomy) is usually curative
- Stage III: Surgery followed by close monitoring or adjuvant therapy in clinical trials
- Stage IV: Systemic therapy, possibly surgery for select patients, palliative care
Active Surveillance
For small tumors (<4 cm) in elderly or ill patients, careful monitoring may be appropriate.
Prevention
While not all kidney cancers can be prevented, you can reduce your risk:
Lifestyle Modifications
- Don't smoke: Quitting smoking reduces risk by up to 50% over time
- Maintain healthy weight: Obesity is a significant risk factor
- Control blood pressure: Through diet, exercise, and medication if needed
- Limit exposure to toxins: Follow safety guidelines for chemical exposure at work
- Stay hydrated: Adequate water intake may help kidney health
- Eat a healthy diet: Rich in fruits and vegetables, low in processed foods
- Exercise regularly: Helps maintain healthy weight and blood pressure
Medical Management
- Regular check-ups if you have risk factors
- Genetic counseling if family history of kidney cancer
- Careful monitoring if you have hereditary syndromes
- Appropriate management of kidney disease
Screening
No routine screening test exists for kidney cancer in average-risk individuals. Those at high risk may benefit from regular imaging.
When to See a Doctor
Make an appointment with your doctor if you experience:
- Blood in your urine (even if intermittent)
- Persistent pain in your side or lower back
- A lump or mass in your side or abdomen
- Unexplained weight loss
- Persistent fatigue
- Recurring fever not due to infection
- Swelling in legs or ankles
Seek immediate medical attention if you have:
- Severe flank pain with fever
- Heavy blood in urine with clots
- Inability to urinate
- Sudden severe swelling in legs
Medical Disclaimer: This information is for educational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of any medical condition.