Renal Tumors



Most renal tumors appear to originate from the tubulointerstitial components of the kidney. Renal cell carcinoma, for instance, is thought to be of proximal tubular origin. The evaluation of a patient for any renal .mass may proceed accord­ing to the scheme given in Figure 34-2. This plan attempts to differentiate benign cystic lesions from solid masses and to identify malignant char­acteristics in solid renal masses.

Benign tumors of the kidney include cortical adenomas and angiomyolipomas (hamartomas). The former are more common in older males and frequently harbor rests of malignant cells. There­fore, adenomas are usually diagnosed after surgical evaluation of a solid renal mass. Angiomy­olipomas are highly vascular fatty tumors that mimic renal cell carcinomas in both presentation and angiographic appearance. A fact of diagnostic significance is the occurrence of over half of these hamartomas in patients with tuberous sclerosis. In patients without tuberous sclerosis, surgical ex­ploration may be necessary for differentiating an-giomyolipoma from renal cell carcinoma if CT scan results are equivocal.

-Renal cell carcinoma, or hypernephroma, is the most frequent malignant renal neoplasm in adults and accounts for about 2 per cent of cancer deaths in both sexes. The term hypernephroma origi­nated from the gross appearance of most of these tumors, which, because of their high lipid con­tent, resemble adrenal tissue.

The classic clinical presentation of renal cell carcinoma is that of a triad of hematuria, flank pain, and palpable flank mass. Actually, only about 10 per cent of patients present with all these features, but any one of these features is present in well over half of all patients as an initial man­ifestation of the tumor. A sizable number of pa­tients will present with nonurinary symptoms, in­cluding fever of unexplained origin, weight loss, and anemia.

Renal cell carcinoma is notable for the large number of extrarenal manifestations of the tumor. Fever is seen in about one fifth of cases and an elevated erythrocyte sedimentation rate (ESR) is seen in half the patients. Anemia is seen in about one third of patients, but polycythemia is a strik­ing finding in some cases. Reversible hepatic dys­function has been described, as has peripheral neuropathy. Ectopic hormone syndromes associ­ated with renal cell carcinoma include hypercal­cemia from osteoclast-stimulating factors (either parathyroid hormone or prostaglandins) and a Cushing syndrome from tumor production of an ACTH-like factor. Hypercalcemia in renal cell car­cinoma is frequently associated with bone metas­tasis of the tumor.

The tumors usually have three cell types: cle?r cells, granular cells, and spindle cells. Tumors composed chiefly of spindle cells and those hav­ing extensive nuclear anaplasia carry a poor prog­nosis. The tumors are highly vascular, supplied by vessels with thin, amuscular walls. Extension of the tumor into normal renal veins and even into the vena cava is not uncommon. Metastatic spread is chiefly via vascular routes, and the lungs, bone, and liver are most frequently sites of metastasis. The tumors often undergo cystic, internal degen­eration, thus mimicking benign renal cysts. Cal­cification within a renal mass is a significant radiographic indicator of malignancy.

As shown in Figure 34-2, needle aspiration of a sonographically cystic lesion is useful in con­firming the diagnosis of a simple renal cyst. Son­ographically solid masses should not undergo needle puncture owing to a risk of rupture of a degenerating carcinoma. Computerized tomogra­phy (CT scan) is the preferred means of examining solid renal masses. Renal cell carcinomas are highly vascular tumors, while avascular masses may be carcinomas (<5 per cent of renal cell tu­mors) or may represent abscesses. Careful needle aspiration for culture may be performed if renal abscess is judged to be likely. Renal arteriography may be important when the CT results are inde­terminate or for delineation of tumor vascular supply.

Treatment of renal cell carcinoma requires sur­gical excision. Vena caval angiography may be valuable preoperatively to ascertain the presence of venous tumor thrombus. Survival is related to cellular morphology, local extension, and distant metastases and ranges from about 10 per cent to about 50 per cent 10-year survival based on these factors.