Types of Kidney Cancer: Understanding the Key Subtypes and Their Impact
A comprehensive guide to the various types of kidney cancer, their characteristics, and why subtype matters for treatment and prognosis.
Types of Kidney Cancer: An In-Depth Overview
Kidney cancer refers to malignant cell growth that arises in the kidney tissues. There are several distinct types and subtypes of kidney cancer, each with different origins, pathological features, and implications for treatment and prognosis. Understanding these types is crucial, as it helps guide therapy choices and provides insight into expected outcomes.
What Is Kidney Cancer?
The kidneys are two bean-shaped organs responsible for filtering blood and producing urine. When abnormal cells in the kidney begin to grow uncontrollably, kidney cancer can develop. While most kidney tumors are malignant, some are benign. Identifying the exact type is essential for accurate diagnosis and treatment planning.
Main Types of Kidney Cancer
- Renal cell carcinoma (RCC): Accounts for about 90% of all kidney cancers in adults. Originates in the renal cortex, specifically in the cells lining the tubules that filter blood and produce urine.
- Urothelial carcinoma (Transitional cell carcinoma): Develops in the renal pelvis, where urine is collected before passing into the ureter. Less common than RCC.
- Wilms’ tumor: The most common kidney cancer in children under five. Rare in adults.
- Renal sarcoma: A rare type that starts in the connective tissue or blood vessels of the kidney.
Renal Cell Carcinoma (RCC): The Most Common Type
RCC, also referred to as renal cell adenocarcinoma, is responsible for the vast majority of adult kidney cancer cases. RCC itself is subdivided into several subtypes based on the appearance and molecular characteristics of the cancer cells under a microscope.
Subtypes of Renal Cell Carcinoma
| Subtype | Percentage of RCC | Distinctive Features | Prognosis |
|---|---|---|---|
| Clear cell RCC | 70-80% | Cells appear clear or pale under the microscope; highly vascular tumors. | 5-year survival rate: ~70% |
| Papillary RCC | 5-10% | Cells form finger-like projections (papillae); divided into type 1 and type 2. | 5-year survival rate: ~90% |
| Chromophobe RCC | 3-5% | Larger cells with pale cytoplasm; less likely to metastasize. | Less aggressive; 7% metastasize |
| Sarcomatoid RCC | ~5% | Cancer cells resemble sarcoma cells; can arise from any type of RCC. | Usually aggressive & advanced at diagnosis |
| Clear cell papillary RCC | 1-4% | Features of both clear cell & papillary RCC; generally indolent. | Excellent prognosis; 2-year survival >90% |
| Collecting duct RCC | <1% | Originates in ducts of Bellini; aggressive, rare. | Poor prognosis; median survival under 1 year |
| Medullary carcinoma | Rare | Primarily in people with sickle cell trait; highly aggressive. | Poor prognosis |
| Mucinous tubular and spindle cell carcinoma (MTSCC) | <0.8% | Low-grade, characterized by tubular and spindle cell structures. | Favorable outcome in most cases |
| Acquired cystic disease-associated RCC (ACDARC) | Rare | Occurs in patients with end-stage renal disease on dialysis with acquired cystic kidney disease. | Variable prognosis |
| Multilocular cystic RCC | 3.1–6% | Cystic in structure; often indolent. | Excellent prognosis |
Clear Cell Renal Cell Carcinoma
Clear cell RCC is by far the most frequent RCC. Cancer cells appear transparent or pale due to the presence of accumulated lipids and carbohydrates. This subtype tends to be highly vascular. While it responds well to certain therapies, the risk of recurrence and metastasis exists, especially in later stages.
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Papillary Renal Cell Carcinoma
Papillary RCC forms about 5–10% of RCC cases and is further divided into:
- Type 1: Cells are small, with scanty cytoplasm.
- Type 2: Larger cells, more aggressive.
These tumors produce papillae – tiny finger-like projections – and usually offer a better prognosis than clear cell RCC.
Chromophobe Renal Cell Carcinoma
This rare form (around 5% of RCCs) is usually less aggressive, with a lower chance to spread (metastasize). Chromophobe RCC cells are distinct for their large, pale appearance. Outcomes tend to be favorable compared to other subtypes.
Less Common and Rare Subtypes of RCC
- Sarcomatoid RCC: Shows features similar to sarcoma (a cancer of connective tissue). This can develop from any RCC subtype and is associated with a rapid progression and a higher likelihood of advanced-stage diagnosis.
- Clear cell papillary RCC: Shares features with both clear cell and papillary types. Usually presents a good prognosis with high survival rates at 2 years.
- Collecting duct RCC: Developing in the collecting ducts which transport urine, this type is highly aggressive and usually diagnosed at an advanced stage. Prognosis is poor, with most patients surviving less than a year.
- Medullary carcinoma: Extremely rare, often occurring in people with sickle cell trait. Known for rapid growth and poor outcomes.
- Mucinous tubular and spindle cell carcinoma (MTSCC): Recognized by tubular and spindle-shaped cells, this low-grade cancer generally has a better outcome.
- Acquired cystic disease-associated RCC (ACDARC): Develops in people on long-term dialysis due to associated cystic kidney disease.
- Multilocular cystic RCC: Makes up about 3%–6% of RCCs, consists of multiple cysts, and usually has an excellent prognosis.
Renal Pelvis Carcinoma (Transitional Cell Carcinoma/Urothelial Carcinoma)
This cancer type accounts for 5–10% of all kidney cancers. It arises from the renal pelvis, the funnel-shaped structure that collects urine within the kidney before it passes into the ureter. Transitional cell carcinoma (TCC) behaves similarly to bladder cancer and is managed with approaches akin to other urothelial malignancies.
Wilms’ Tumor
Wilms’ tumor (nephroblastoma) is the most common kidney cancer affecting children, usually those under 5 years of age. Rarely, it can appear in adults. Many cases are diagnosed before spreading, and treatment often yields a very good prognosis, especially with early detection and modern therapies.
Renal Sarcoma
Comprised of less than 1% of all kidney cancers, renal sarcoma originates in the connective tissues—such as fat, muscle, or blood vessels—of the kidney. It is aggressive and frequently presents at an advanced stage, requiring intensified treatment strategies.
Rare Kidney Tumors and Benign Lesions
Some rare kidney tumors and benign masses, although not considered cancer, may initially be mistaken for malignant tumors due to similar imaging characteristics. Some notable examples include:
- Oncocytomas: Non-cancerous tumors arising from the collecting ducts, typically requiring surgical removal if large or symptomatic.
- Angiomyolipomas: Benign tumors composed of blood vessels, muscle cells, and fat; usually managed without surgery unless symptomatic or large.
- Renal cysts: Fluid-filled sacs are common and frequently benign; complex cysts may require further evaluation.
Why Does the Type of Kidney Cancer Matter?
Knowing the specific type and subtype of kidney cancer is crucial because:
- Treatment choices—such as surgery, immunotherapy, targeted therapy, and chemotherapy—depend on the subtype.
- Prognosis (chance of recovery) varies greatly among different subtypes.
- The risk of recurrence, spread (metastasis), and response to treatment are influenced by cancer type.
- Understanding the subtype guides monitoring and follow-up recommendations.
Symptoms and Risk Factors of Kidney Cancer
Most kidney cancers are found incidentally during imaging for other reasons. However, some common symptoms include:
- Blood in the urine (hematuria)
- Pain in the flank (side or back)
- Lump or mass in the kidney area
- Unexplained weight loss
- Fatigue
- Fever not attributable to infection
Risk factors for kidney cancer include:
- Smoking
- High blood pressure
- Obesity
- Family history of kidney cancer
- Prolonged exposure to certain toxins (asbestos, cadmium, some herbicides)
- Long-term dialysis
- Certain inherited syndromes (Von Hippel-Lindau disease, hereditary papillary RCC, etc.)
Treatment Approaches by Cancer Type
Treatments vary depending on the subtype, grade, and extent of spread. Broad strategies include:
- Surgical removal (partial or radical nephrectomy) for localized cancers
- Immunotherapy for advanced or metastatic disease
- Targeted therapies for certain molecularly driven cancers
- Chemotherapy (mainly for Wilms’ tumor or rare subtypes)
- Active surveillance for small, indolent tumors or in high-risk surgical patients
Frequently Asked Questions (FAQs)
Q: Which type of kidney cancer is most common?
A: Renal cell carcinoma (RCC) accounts for approximately 90% of all adult kidney cancers.
Q: What is the best treatment for kidney cancer?
A: Treatment depends on the cancer type, stage, and patient health. Surgery is most common for localized disease, while targeted therapies and immunotherapy are used for advanced RCC. Wilms’ tumor in children is typically treated with surgery and chemotherapy.
Q: How do I know which kidney cancer type I have?
A: Diagnostic evaluation, including imaging, biopsy, and sometimes genetic testing, helps determine the cancer’s exact type and grade. Your healthcare team will review pathology results and discuss your subtype.
Q: Can kidney cancer be inherited?
A: Yes, several hereditary syndromes increase kidney cancer risk, such as Von Hippel-Lindau disease and hereditary papillary RCC. If you have a strong family history, genetic counseling may be advised.
Q: Are all kidney tumors cancerous?
A: No. Some kidney tumors, such as oncocytomas and angiomyolipomas, are benign. Diagnostic imaging and, in some cases, biopsy can clarify whether a tumor is malignant or benign.
Summary
There are several types and subtypes of kidney cancer, each with distinctive characteristics, causes, and implications for treatment and prognosis. The majority are renal cell carcinomas, with multiple subtypes determined by their cellular appearance and genetics. Less common types include tumors of the renal pelvis, sarcomas, and Wilms’ tumor in children. Accurate diagnosis is key to determining optimal treatment and improving outcomes.
References
- https://www.healthline.com/health/kidney-cancer
- https://www.cancerresearchuk.org/about-cancer/kidney-cancer/stages-types-grades/types-grades
- https://www.healthline.com/health/kidney-cancer/kidney-cancer-types
- https://www.mskcc.org/cancer-care/types/kidney/types
- https://www.medicalnewstoday.com/articles/types-of-kidney-cancer
- https://www.youtube.com/watch?v=oZP1MwIifpU
- https://www.healthline.com/health/video/kidney-failure
- https://www.cancer.org/cancer/types/kidney-cancer.html
- https://my.clevelandclinic.org/health/diseases/9409-kidney-cancer-overview
- https://www.mayoclinic.org/diseases-conditions/kidney-cancer/symptoms-causes/syc-20352664
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