Kidney cancer, also known as renal cancer, is a group of cancers that start in the kidney. Symptoms may include blood in the urine, a lump in the abdomen, or back pain. Fever, weight loss, and tiredness may also occur. Complications can include spread to the lungs or brain. The main types of kidney cancer are renal cell cancer (RCC), transitional cell cancer (TCC), and Wilms' tumor. RCC makes up about 80% of kidney cancers, and TCC accounts for most of the rest. Risk factors for RCC and TCC include smoking, certain pain medications, previous bladder cancer, being overweight, high blood pressure, certain chemicals, and a family history. Risk factors for Wilms' tumor include a family history and certain genetic disorders such as WAGR syndrome. Diagnosis may be suspected based on symptoms, urine testing, and medical imaging. It is confirmed by tissue biopsy. Treatment may include surgery, radiation therapy, chemotherapy, immunotherapy, and targeted therapy. Kidney cancer newly affected about 403,300 people and resulted in 175,000 deaths globally in 2018. Onset is usually after the age of 45. The overall five-year survival rate is 78% in the United States and 73% in Canada. Using older statistics from 2017 and 2018, the survival rate was 70% in China, and 60% in Europe. For cancers that are confined to the kidney, the five-year survival rate is 93%; if it has spread to the surrounding lymph nodes, it is 76%, and if it has spread widely, it is 19%. Kidney cancer has been identified as the 13th-most-common form of cancer, and is responsible for 2% of the world's cancer cases and deaths. The incidence of kidney cancer has continued to increase since 1930. Renal cancer is more commonly found in populations of urban areas than rural areas.
Signs and symptoms Early on, kidney masses do not typically cause any symptoms and are undetectable on physical examination. As kidney cancer becomes more advanced, it classically results in blood in the urine, flank or back pain, and a mass. Other symptoms consistent with advanced disease include weight loss, fever, night sweats, palpable swollen lymph nodes in the neck, nonreducing varicocele, bone pain, continuous cough, and bilateral lower-leg swelling.
Paraneoplastic syndromes caused by kidney cancer can be broadly classified as endocrine or nonendocrine. Endocrine dysfunctions include increase in blood calcium levels (hypercalcemia), high blood pressure (hypertension), increased red blood cells (polycythemia), liver dysfunction, milky nipple discharge unrelated normal breast-feeding (galactorrhea), and Cushing's syndrome. Nonendocrine dysfunctions include deposition of protein in tissue (amyloidosis), decrease in hemoglobin or red blood cells (anemia), disorders of nerves, muscles (neuromyopathies), blood vessels (vasculopathy), and blood clotting mechanisms (coagulopathy).
Causes Factors that increase the risk of kidney cancer include smoking, high blood pressure, obesity, faulty genes, a family history of kidney cancer in first-degree relatives, having kidney disease that needs dialysis, being infected with hepatitis C, and previous treatment for testicular or cervical cancer. Also, other possible risk factors, such as kidney stones, are being investigated. About 25–30% of kidney cancer is attributed to smoking. Smokers have a 1.3 times higher risk of developing kidney cancer compared to nonsmokers. Moreover, an increased risk of cancer development is dose-dependent; men who smoke more than 20 cigarettes per day have twice the risk. Likewise, women who smoke more than 20 cigarettes per day have 1.5 times the risk of nonsmoking women. After 10 years of smoking cessation, a substantial reduction is seen in the risk of developing kidney cancer.
Diagnosis Due to the increase in ultrasound and CT imaging for nonspecific abdominal complaints, kidney masses are frequently incidentally diagnosed on medical imaging. More than 60% of renal cell carcinomas (the most common type of kidney cancer) are diagnosed incidentally by abdominal imaging for nonspecific abdominal complaints. Kidney masses can be classified by the nature of the cells in the growth, or by their appearance on radiography. The term cancer refers to a malignant tumor, which is an uncontrolled growth of abnormal cells, in this case being a kidney tumor.
Medical imaging Since the differential diagnosis for a kidney tumor is large, the first step is to characterize the mass with medical imaging to assess whether it is benign or malignant. Ultrasonography is sometimes used to evaluate a suspected kidney mass, as it can characterize cystic and solid kidney masses without radiation exposure and at relatively low cost. Radiologically, kidney tumors are grouped based on appearance into simple cystic, complex cystic, or solid. The most important differentiating feature of a cancerous and noncancerous tumor on imaging is enhancement. Simple cysts, which are defined by strict criteria, are safe to be monitored if the person does not have any symptoms. However, all masses that are not clearly simple cysts should be further evaluated and confirmed by alternate imaging techniques. Computed tomography (CT) of the abdomen administered with and without intravenous contrast is the ideal imaging method to diagnose and determine the stage of kidney cancer. Tentative evidence indicates that iodinated contrast agents may cause worsening of kidney function in people with chronic kidney disease with a glomerular filtration rate less than 45 ml/min/1.73 m2 and should therefore be given cautiously to such persons. Abdominal magnetic resonance imaging (MRI) is an alternative imaging method that can be used to characterize and stage a kidney mass, and may be suggested if contrast material cannot be given. MRI can also evaluate the inferior vena cava if the mass is suspected to extend outside the kidney. Since the lungs are the most common organ for kidney cancer metastasis, a chest X-ray or CT scan may be ordered based on the person's risk for such disease.
Histopathologic classification
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