Mortality

Rates And Ratios

Age

Special note must be made of Wilms' tumors of the kidney which are found almost exclusively in children, average age at diagnosis being under 3 years. Wilms' tumors comprise 5 to 10% of all kidney cancers.

Trend Last Ten Years

Geographic Distribution And Other Factors

Aside from the unexplained male-female ratio, there is no suggestive epidemiologic evidence showing variation in the distribution of kidney cancer in relation to geographic area, nationality, etc.

Etiology

In the vast majority of cases of kidney cancer, no etiology is apparent.

There appears to be widespread agreement that the relatively rare squamous carcinoma of the renal pelvis is frequently associated with chronic infection and stone formation. The latter is thought to antedate the neoplasm and predispose to its development. Also, known bladder carcinogens are apparently capable of producing tumors of the renal pelvis, but they account for only a small fraction of such lesions.

Pathology

Kidney tumors may arise from the renal parenchyma (85%) or pelvis (15%) (Fig. 76).

Fig. 76. Site of origin of kidney tumors.

Renal Parenchyma

1. These are most accurately known as renal cell carcinomas but often are referred to as hypernephromas.

2. They make up approximately 85% of all kidney tumors. Grossly they have the following characteristics:

1. Well demarcated, sometimes with a capsule

2. Usually quite large at time of diagnosis

3. Often round and lobulated

4. Bright yellow on cross section

Microscopically they are adenocarcinomas of one of the following three types:

1. Clear cell type

2. Granular cell variety

3. Mixtures of both

Direct extension into the renal pelvis is a late finding; they metastasize most commonly to:

1. Lung

2. Bone

3. Liver

Wilms' tumor

Included under the heading of tumors of the renal parenchyma is the Wilms tumor. This differs in many respects from lesions of the type just described both pathologically and clinically.

1. It is thought to arise from the renal anlage and thus is often referred to as embryonal carcinoma.

2. Wilms' tumor is found almost exclusively in children, usually under the age of 7 years. The average age at diagnosis is 2 to 3 years.

3. The ratio of males to females is about equal.

4. The tumor grows with great rapidity and may attain massive size in a matter of weeks.

5. It is usually present as a painless abdominal mass discovered by the mother while bathing the child or by the physician while examining routinely or for intercurrent illness.

6. Hematuria is quite uncommon.

7. Weight loss, anemia, weakness, and various gastrointestinal symptoms may be prominent and early symptoms.

8. Although nephrectomy with preoperative or postoperative x-ray therapy is the primary form of treatment, response to x-ray therapy and to some chemotherapeutic agents, particularly actinomycin D, may be striking, though usually transient. Five-year survival rates are in the range of 25%.

Renal Pelvis

The surface of the renal pelvis is best thought of as a close counterpart of bladder transitional epithelium.

Tumors in this area are subdivided into two types:

1. Papillary-80 to 90%

2. Nonpapillary (epidermoid or squamous)-10 to 20% Papillary

1. Arise from transitional epithelium and are by far the more common, outnumbering the squamous variety nearly 10 to 1.

2. Sometimes multiple, soft, branching lesions, red, pink, or gray in color.

3. May be difficult to decide which are malignant, even microscopically (situation is analogous to that of bladder papillomas); they are all, therefore, treated as malignant or potentially so.

4. No apparent association with chronic infection and stones.

5. Often (one third of the cases) associated with a similar lesion in the ureter and bladder, either at time of diagnosis or at some time in the follow-up.

6. Sometimes (about 5%) bilateral.

7. Distant metastases uncommon.

8. May result from action of extrinsic carcinogens as in the bladder.

Nonpapillary (Epidermoid Or Squamous)

1. Quite rare.

2. A flat, indurated, ulcerating lesion, grayish-white in color.

3. Usually well advanced at time of discovery.

4. When present, it is often associated with chronic infection and stones; leukoplakia of the renal pelvis may be present.

5. May result from action of extrinsic carcinogens as in the bladder, although evidence is lacking in this regard.

6. A highly malignant tumor with a very poor prognosis.

7. Tendency toward local invasion and distant metastasis. Both types of renal pelvis cancers may give rise to the following:

1. Obstruction of the urinary tract, usually at the level of the ureter or ureteropelvic junction, although more localized calyceal functional impairment may occur.

2. Infection, usually secondary to obstructive phenomena.

3. Hemorrftage of significant degree into urinary tract.

Screening Presumably Well Adults For Renal Cancer-Detection

Certain parts of the routine cancer detection examination performed on presumably healthy adults are designed to screen for kidney cancer.

1. The review of systems may elicit urinary symptoms that have been noted by the patient but regarded as insignificant.

2. Special situation. An individual who by reason of occupation, hobby, or otherwise has a history of exposure to known or suspected urinary carcinogens should be earmarked for more frequent and intensive routine survey (see bladder cancer, p. 240 ff.).

3. Physical examination of the abdomen (inspection and palpation) may reveal the presence of a mass in the right or left upper quadrant and flank. This should always raise the question of a kidney tumor.

4. Urinalysis may reveal the presence of gross or microscopic hematuria upon examination of the urinary sediment. A tumor at some point in the urinary tract must be ruled out under these circumstances.

5. The hemoglobin determination may reveal the presence of anemia in the asymptomatic patient. Renal cancer sometimes is first manifested by occult and unexplained anemia. Rarely the reverse is true and a kidney tumor is associated with polycythemia or a leukemoid reaction.