Kidney Tumors
BENIGN SOLID TUMORS
Renal Cortical Adenomas
Renal cortical adenomas are benign tumors of the renal cortex that are generally discovered incidentally. They have been distinguished from renal cell carcinomas (RCCs) in the past primarily by their small size: <3 cm in diameter. The designation of these tumors as benign adenomas has been questioned because they are histologically indistinguishable from RCCs. It has been reasoned that all tubular cell adenomas are malignant and simply represent an early stage of renal carcinoma growth. These tumors should be treated as small indolent RCCs.
Renal Oncocytoma
Renal oncocytoma is generally a benign, unifocal renal tumor that averages 5 to 8 cm in diameter with a higher incidence in older patients; however, the presence of malignant elements has been known to occur. Its presentation is usually discovered incidentally and is clinically and radiographically indistinguishable from RCC. It can have a somewhat typical “spoke-wheel” appearance on angiogram, but this is uncertain. If an oncocytoma is suspected, a core needle biopsy may be beneficial. Partial or radical nephrectomy is the safest method of treatment because of the unreliability of differentiating it from RCC preoperatively.
Angiomyolipomas (Renal Hamartoma)
Angiomyolipomas are generally benign tumors, frequently bilateral or multiple, and are often associated with tuberous sclerosis. Histologically, they are composed of fat cells, blood vessels, and sheets of smooth muscle cells. Profuse internal hemorrhage can occur. Its angiographic pattern is not characteristic; however, it has a distinctive fat content on computed tomography (CT) that is usually diagnostic. Asymptomatic lesions smaller than
4 cm should be followed with yearly ultrasound. Larger tumors should be considered for embolization or renal-sparing surgery. Conservative surgical therapy is necessary because of frequent bilaterality and multiplicity.
4 cm should be followed with yearly ultrasound. Larger tumors should be considered for embolization or renal-sparing surgery. Conservative surgical therapy is necessary because of frequent bilaterality and multiplicity.
Other Rare Benign Renal Tumors
Fibroma, lipoma, leiomyoma, angioma, rhabdomyoma, neurofibroma, dermoid tumors, and tumors of endometriosis are other rare benign renal tumors.
Pseudotumors
Pseudotumors are normal variants of functioning renal tissue that can occasionally appear as a questionable renal mass on intravenous (IV) urography or ultrasound. They include fetal lobulations, column of Bertin, dromedary hump, hilar lip or uncus, and nodular compensatory hypertrophy. A CT scan will generally differentiate a true tumor from a pseudotumor. However, if one suspects an equivocal renal mass to be a pseudotumor, then a DMSA (dimercaptosuccinic acid) renal scan may be helpful. A pseudotumor will appear as normal homogeneous functioning kidney, whereas a true renal mass will appear as a focal defect within the renal parenchyma (sensitivity 95%).
MALIGNANT TUMORS
Renal Cell Carcinoma (Hypernephroma and Renal Adenocarcinoma)
RCC is the most common solid renal tumor (85%). It is primarily a tumor of adults (average age early sixties). Approximately 50,000 new diagnoses are made each year in the United States and 13,000 deaths from it are recorded. RCCs arise from renal tubular epithelial cells commonly of the proximal convoluted segment with no known cause. These are typically round tumors of varying size with a pseudocapsule and areas of hemorrhage and necrosis, and they often displace or invade the collecting system. Local extension occasionally occurs despite Gerota’s fascia. Tumor thrombus into the renal vein is frequent and may extend into the vena cava. Metastatic spread is to the lung, liver, bone, brain, and subcutaneous tissues.
Pathologic subtypes of renal tumors include clear cell (70%-80%), papillary (10%-15%), chromophobe (5%), collecting duct (<1%), and unclassified RCC. Sarcomatoid elements in 1% to 5% of RCCs indicate a poor prognosis.
▪ Etiology
Tobacco use and obesity are the most consistently identified risk factors for RCC. Hypertension also increases the risk of developing RCC. No occupational risk factors have been identified.
▪ Presentation
Because of its retroperitoneal location, symptoms such as the classic triad of pain, hematuria, and flank mass occur only rarely today and generally indicate advanced disease. More than 50% of these tumors are presenting as asymptomatic incidental findings on abdominal ultrasound or CT scans. Nevertheless, the more frequent findings are pain (41%), hematuria (36%), weight loss (36%), flank mass (24%), hypertension (20%), hypercalcemia (13%), and erythrocytosis (3%). Some paraneoplastic syndromes may occur as a result of renal tumor production of 1,25-dihydroxycholecalciferol, rennin, erythropoietin, and other hormone substances. Hepatic dysfunction without the evidence of hepatic metastasis (Stauffer’s syndrome) can occur in up to 20% of patients. Epidemiologic studies suggest tobacco smoking as a likely cause.
Patients with Von Hippel-Lindau disease frequently get RCC in addition to pheochromocytomas, retinal angiomas, and hemangioblastomas of the brain and spinal cord.
▪ Diagnosis
The renal tumor must first be differentiated from the more common benign renal cysts. Ultrasound and CT scan can effectively define the solid or cystic nature of the mass. CT scan both prior to and following IV contrast is the standard diagnostic technique. Magnetic resonance imaging (MRI) is reserved for the clinical settings of locally advanced malignancy, possible vein involvement, renal insufficiency, or allergy to IV contrast. Complete evaluation of the cystic renal mass is described in Chapter 15. Percutaneous biopsy or fine needle aspiration of a solid renal mass traditionally had little value except when lymphoma or metastases to the kidney is suspected from another
primary. However, recent data on renal biopsy demonstrated improved accuracy and safety with only 1% false-negative rate and <2% complication rate requiring any form of intervention. Since 20% of clinical stage T1 renal masses are benign, renal biopsy should be considered if less aggressive management is being considered.
primary. However, recent data on renal biopsy demonstrated improved accuracy and safety with only 1% false-negative rate and <2% complication rate requiring any form of intervention. Since 20% of clinical stage T1 renal masses are benign, renal biopsy should be considered if less aggressive management is being considered.
Abdominal Computed Tomography
A CT scan without and with IV contrast (renal protocol) is the method of choice to evaluate a renal mass. Any mass that enhances with IV contrast should be considered a RCC until proven otherwise. CT also provides accurate information on renal vein and inferior vena cava involvement, lymph node metastases, and perirenal extension to adjacent organs.
Magnetic Resonance Imaging
MRI can help differentiate solid and cystic renal masses and is particularly useful in patients who cannot receive IV contrast agents. Enhancement following IV GDPA (gadolinium diethylenetriamine pentaacetic acid) on T1 images of an MRI indicates vascularity and helps identify RCC. MRI has become the best study to evaluate the IVC (inferior vena cava) for tumor thrombus.
Selective Renal Arteriography
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
