Introduction
Background
Renal cell carcinoma (RCC) is the most common primary renal malignant neoplasm in adults. It accounts for approximately 85% of renal tumors and 2% of all adult malignancies. RCC is more common in men than in women (ratio, 2:1), and it most often occurs in patients aged 50-70 years. Approximately 38,890 new cases of RCC and 12,840 deaths are expected in the United States in 2006. One fourth to one third of patients present with metastatic disease. In only approximately 2% of cases are bilateral tumors seen at presentation. Risk factors include increased age; male sex; smoking; cadmium, benzene, trichloroethylene, and asbestos exposure; excessive weight; chronic dialysis use; and several genetic syndromes (familial RCC, hereditary papillary RCC, von Hippel-Lindau syndrome, and tuberous sclerosis).
Pathophysiology
RCCs arise from the tubular epithelium and are usually based in the renal cortex. Several pathologic subtypes have been described, including the clear cell, papillary, granular cell, chromophobe cell, sarcomatoid, and collecting duct subtypes. These tumors vary from being nearly completely cystic to being completely solid. The imaging features reflect this heterogeneity. Bilateral RCCs are common in von Hippel-Lindau syndrome, tuberous sclerosis, and chronic dialysis; however, bilateral RCCs occur in only approximately 2% of cases. RCCs are multicentric in as many as 25% of patients.
Spread by means of direct local invasion of adjacent structures, such as the adrenal glands, liver, spleen, colon or pancreas, can occur. Local regional lymph node metastases are also common. RCCs have a propensity to extend into the renal vein and, subsequently, into the inferior vena cava. The lungs are the most common sites of distant metastases. Liver, bone, adrenal gland, and kidney metastases may also occur. Typically, skeletal metastases are purely lytic.
RCCs can be staged by using the American Joint Committee on Cancer TNM (T umor, N ode, M etastases) classification, as follows:
- Stage 1 RCCs are 7 cm or smaller and confined to the kidney.
- Stage 2 RCCs are larger than 7 cm but still organ confined.
- Stage 3 tumors extend into the renal vein or vena cava, involve the ipsilateral adrenal gland and/or perinephric fat, or have spread to one local lymph node.
- Stage 4 tumors extend beyond the Gerota fascia, to more than one local node or have distant metastases.
Recent literature has questioned whether the cutoff in size for stage 1 and 2 tumors should be 5 cm instead of 7 cm.
Frequency
United States
RCC accounts for approximately 2% of adult malignancies, with about 38,890 new cases and 12,840 deaths expected in the United States in 2006. Small RCCs are found at autopsy in as many as 22% of cases.
Mortality/Morbidity
The prognosis of patients with RCC depends on its stage at diagnosis.
- The prognosis is worst for patients with metastatic disease at presentation and best for patients with small masses confined to the kidney.
- The size of the primary lesion also affects the prognosis because larger lesions tend to be higher grade and metastasize more frequently. Poorly marginated or necrotic lesions also tend to be of higher grade.
- If resection is attempted, the 5- and 10-year survival rates for stage T1 cancers are 95% and 91%, respectively. For T2 cancers, the 5- and 10-year survival rates are 80% and 70%, respectively. Unresectable RCCs are associated with a 5-year survival rate of less than 20%.
Race
No significant differences in incidence based on race are reported.
Sex
RCC is more common in men than in women, with a male-to-female ratio of approximately 2:1.
Age
The incidence peaks in patients aged 50-70 years, but the age distribution is broad. RCC rarely occurs in young children and is uncommon in adults younger than 45 years.
Anatomy
The kidney is a retroperitoneal structure surrounded by a fibrous capsule and enclosed in the perirenal space with the adrenal gland and fat. In the general population, 70%-80% of individuals have single renal arteries to each kidney. The remaining population has multiple renal arteries. Multiple renal veins are rarer, occurring in approximately 10% of patients. The vascular anatomy becomes important whenever minimally invasive surgery or nephron-sparing surgery is considered because control of potentially bleeding vessels is paramount.
Presentation
Clinically, patients present with hematuria, flank pain, or (less frequently than in the past) a flank mass. Currently, nearly half of RCCs are discovered incidentally during imaging for indications other than the assessment of RCC. In one series, 0.3% of all CT scans demonstrated incidental RCC. Incidental detection has also increased on ultrasound (US) images. Occasionally, patients present with systemic symptoms such as fever, nausea, anorexia, and weight loss. Rarely, patients have symptoms related to humoral factors such as parathormone, prolactin, erythropoietin, or renin.
Preferred Examination
Although a variety of examinations (ultrasound [US], magnetic resonance imaging [MRI], angiography) can be used in the workup of patients with suspected RCC, the preferred method of imaging these patients is dedicated renal computed tomography (CT). In most cases, this single examination can be used to detect and stage RCC and to provide information for surgical planning without additional imaging.
In the few patients in whom the CT findings are equivocal, MRI or US can be useful. Recent literature suggests a use for contrast-enhanced Doppler US for lesions that show equivocal enhancement at CT. Angiography is rarely used in the workup of suggested RCC, but it can provide information about the origin of the tumor in troublesome cases. At present, no accepted protocol has been developed for RCC screening among asymptomatic individuals in the general population. Patients with a hereditary predisposition for RCC should be periodically examined by using dedicated renal CT.
Limitations of Techniques
The primary limitation of CT is the characterization of hypoattenuation in masses smaller than 8-10 mm, in which pseudoenhancement may be a problem. In these cases, US may be of some use in characterizing the lesions as cysts. In addition, spread to regional lymph nodes in the absence of lymph node enlargement can be missed. If contrast material cannot be intravenously administered, CT is a poor choice for evaluating RCCS. MRI should be performed instead.The primary limitations of US include problems related to incomplete staging (bones, lungs, regional nodes) and to the detection of small non–contour-deforming masses. In addition, large patients are not good candidates for US because of technical difficulties in obtaining adequate images.
MRI is limited by patient cooperation because MRI is more sensitive to motion artifact than CT. In addition, MRI is more expensive and less readily available than CT. Furthermore, patients with pacemakers, those with certain types of medical implants, and those with severe claustrophobia are excluded from undergoing MRI.
Patient Education: For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see eMedicine's patient education article Renal Cell Cancer.
Differential Diagnoses
Other Problems to Be Considered
Angiomyolipoma
Collecting duct carcinoma
Hemorrhagic cyst
Infected cyst
Lymphoma
Metastatic disease
Oncocytoma
Renal abscess
Transitional cell carcinoma
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Further Reading
Keywords
renal adenomas, clear cell carcinomas, RCC, hypernephromas, kidney cell carcinoma, kidney carcinoma, nephric carcinoma, nephric cell carcinoma, renal cancer, kidney cancer, nephric cancer, renal cancer, kidney cell cancer
