Non-RCC Renal Malignancies

Sarcomas of the Kidney

Renal sarcoma is less common but more lethal than sarcoma of any other genitourinary site

High-grade sarcomas often metastasize, with the lungs being a primary site of spread, and prognosis is poor; many patients die of disease progression in a matter of months.
- Sarcomas are derived from mesenchymal components and are thus free of many of the natural barriers to dissemination that confine other tumor types.
Low-grade sarcomas tend to pursue a more indolent course

Signs and Symptoms (similar to those seen with large, rapidly growing RCCs)
- Palpable mass
- Abdominal or flank pain
- Hematuria
Differentiation of renal sarcoma from sarcomatoid RCC is often difficult on the basis of clinical presentation, radiographic findings, and, in some cases, pathologic analysis

The initial resection is the key event because this is the best chance for a long-term cure. This often mandates RN along with en bloc excision of adjacent organs. This is primarily a surgical disease, and wide excision is the goal with intraoperative monitoring of margin status. Chemotherapeutic agents that have demonstrated activity against metastatic sarcomas, but even in the best of circumstances response rates are disappointing. The combination of radiation therapy and chemotherapy, which has proved effective in an adjuvant setting for the management of sarcomas of the extremity, has not provided much benefit for renal or retroperitoneal sarcomas. At present, the role of such adjuvant approaches for the management of renal sarcomas is not well defined, although a multimodal approach is often pursued if performance status allows, given the poor prognosis.

The most important prognostic factors for sarcomas are margin status and tumor grade

Renal involvement with hematologic malignancies, which include the lymphomas and leukemias, is common
- The most common hematologic malignancy to involve the kidney is lymphoma
Renal lymphoma should be suspected in patients with (4):
1. Infiltrative renal lesions
2. Splenomegaly
3. Lymphadenopathy that is out of proportion to the renal primary
4. Lymphadenopathy in other regions of the body or atypical regions within the retroperitoneum
  - Lymphadenopathy centered outside of the main landing zones (see above) should raise suspicion for lymphoma
The radiographic patterns manifested by renal lymphoma are diverse and can be difficult to differentiate from RCC
Any patient with a prior history of lymphoma and a renal mass should also be evaluated for renal recurrence rather than for RCC.

Renal involvement related to leukemia is more common in children
Renal lymphoma and leukemia are commonly silent but can be associated with hematuria, flank pain, or progressive renal failure. Fever, weight loss, and fatigue, the so-called B symptoms of lymphoma, are much more common
If lymphoma or leukemic renal involvement is suspected, consideration should be given to percutaneous biopsy or aspiration to obtain a pathologic diagnosis
Extirpative surgery should be avoided if renal lymphoma and leukemia are suspected because the primary treatment of these processes is systemic chemotherapy with or without radiation therapy
- Nephrectomy is seldom indicated except in patients with severe symptoms, such as uncontrollable hemorrhage.
- The other notable exception is the extremely rare patient with primary renal lymphoma in whom a combination of nephrectomy and systemic chemotherapy may represent optimal therapy

Metastatic tumors are the most common malignant neoplasms in the kidney, outnumbering primary renal tumors by a wide margin. Autopsy studies have shown that 12% of patients dying of cancer have renal metastases, making the kidney one of the most common sites for metastatic dissemination. The profuse vascularity of the kidney makes it hot spot for the deposition and growth of cancer cells.
The most frequent sources of renal metastases include lung, breast, and gastrointestinal cancers, malignant melanoma, and the hematologic malignant neoplasms
Metastases to the kidney are often multifocal, poorly enhancing, and infiltrative rather than well demarcated, although there are exceptions to these rules.
Renal metastases should be suspected in any patient with multiple renal lesions and widespread systemic metastases or a history of nonrenal primary cancer. If there is any uncertainty about the diagnosis, percutaneous renal biopsy usually provides pathologic confirmation

Carcinoid tumors
- Arise from neuroendocrine cells, which are not normally present in the kidney.
- An association with horseshoe kidneys has been reported.
- Measurement of urinary or plasma serotonin or its metabolites can be diagnostic.
- Only a minority of patients will present with the carcinoid syndrome—episodic flushing, wheezing, and diarrhea.
- Surgical excision is the mainstay of treatment
- Generally good prognosis
Multimodal therapy should be considered for renal small cell carcinoma, round cell or Ewing’s family of tumours, or adult Wilm’s tumours.

Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 57