Wilms Tumor and Other Childhood Kidney Tumors Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Stage Information
For patients with suspected Wilms tumors, preoperative staging studies should include a computed tomography (CT) scan of the abdomen/pelvis and chest. Preoperative assessment of intravascular extension of Wilms tumor is essential to guide management. The presence of intravenous tumor thrombus, which has been reported in up to 11.3% of Wilms tumor cases, can lead to differences in management. In North America, local staging of Wilms tumor is performed with CT or magnetic resonance imaging of the abdomen and pelvis. Contrast-enhanced CT has high sensitivity and specificity for detection of cavoatrial tumor thrombus in Wilms tumor cases that may impact surgical approach. Routine Doppler evaluation after CT has been performed is not required.
The stage is determined by the results of the imaging studies and both the surgical and pathologic findings at nephrectomy and is the same for tumors with favorable or anaplastic histology. Thus, patients should be characterized by a statement of both criteria (for example, stage II, favorable histology or stage II, anaplastic histology).[2,3]
The staging system was originally developed by the National Wilms Tumor Study Group and still used by the Children's Oncology group. The staging system and incidence by stage are outlined below.
In stage I Wilms tumor (43% of patients), all of the following criteria must be met:
Tumor is limited to the kidney and is completely resected.
The renal capsule is intact.
The tumor is not ruptured or biopsied prior to removal.
No evidence of the tumor at or beyond the margins of resection.
For a tumor to qualify for certain therapeutic protocols as stage I, regional lymph nodes must be examined microscopically.
In stage II Wilms tumor (20% of patients), the tumor is completely resected, and there is no evidence of tumor at or beyond the margins of resection. The tumor extends beyond the kidney as evidenced by any one of the following criteria:
There is regional extension of the tumor (i.e., penetration of the renal sinus capsule, or extensive invasion of the soft tissue of the renal sinus, as discussed below).
Blood vessels within the nephrectomy specimen outside the renal parenchyma, including those of the renal sinus, contain tumor.
Rupture or spillage confined to the flank, including biopsy of the tumor, is no longer included in stage II and is now included in stage III.
In stage III Wilms tumor (21% of patients), there is residual nonhematogenous tumor present following surgery that is confined to the abdomen. Any one of the following may occur:
Lymph nodes within the abdomen or pelvis are involved by tumor. (Lymph node involvement in the thorax or other extra-abdominal sites is a criterion for stage IV.)
The tumor has penetrated through the peritoneal surface.
Tumor implants are found on the peritoneal surface.
Gross or microscopic tumor remains postoperatively (e.g., tumor cells are found at the margin of surgical resection on microscopic examination).
The tumor is not completely resectable because of local infiltration into vital structures.
Tumor spillage occurs either before or during surgery.
The tumor is treated with preoperative chemotherapy and was biopsied (using Tru-cut biopsy, open biopsy, or fine-needle aspiration) before removal.
The tumor is removed in more than one piece (e.g., tumor cells are found in a separately excised adrenal gland; a tumor thrombus within the renal vein is removed separately from the nephrectomy specimen). Extension of the primary tumor within vena cava into thoracic vena cava and heart is considered stage III, rather than stage IV, even though outside the abdomen.