Wilms' tumor other diagnostic studies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shanshan Cen, M.D. [2]

Overview

18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT and biopsy may be helpful in the diagnosis of wilms' tumor.

Other Diagnostic Studies

Other diagnostic studies for wilms tumor include:

• PET scan
  • 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET)-CT.
  • Wilms tumor is 18F-FDG avid, and 18F-FDG-PET-CT imaging adds clinically applicable information to conventional imaging.
  • This may be particularly helpful in patients with bilateral disease or those receiving preoperative chemotherapy.
  • 18F-FDG-PET-CT highlights FDG-avid areas in the tumor and metastases.
  • This corresponds to histologically confirmed active disease.

Biopsy

Biopsy or resection. In children with a renal mass that clinically appears to be stage I or stage II Wilms tumor, biopsy is not performed so that tumor cells are not spread during the biopsy. A biopsy would upstage such a patient to stage III. Nephrectomy (in North America) or chemotherapy (in Europe) is performed instead. Therefore, the diagnostic pathology is first seen when the nephrectomy specimen is examined.

Biopsy of a renal mass may be indicated if the mass is atypical by radiographic appearance for Wilms tumor, and the patient is not going to undergo immediate nephrectomy. Biopsy tissue from inoperable Wilms tumor obtained before chemotherapy may be used for histologic review and initial treatment decisions. The use of biopsy to determine histology in an inoperable tumor remains controversial because biopsy may cause local tumor spread. It is important to recognize that data from NWTS-4 and NWTS-5 (COG-Q9401/NCT00002611) have shown conclusively that, because of histologic heterogeneity of Wilms tumor, a significant number of patients have unfavorable histology that is missed during an upfront biopsy but revealed at the time of definitive surgery following chemotherapy.

If the initial imaging studies suggested a possible lesion on the contralateral kidney, the contralateral kidney is formally explored to rule out bilateral involvement. This is done before nephrectomy to exclude bilateral Wilms tumor.

Biopsy is also controversial in patients with bilateral tumors because biopsy rarely detects anaplasia in bilateral Wilms tumor, and the incidence of bilateral tumors being other than Wilms is very low. The current COG study of bilateral Wilms tumor and of patients with unilateral Wilms tumor predisposed to developing bilateral tumors tries to avoid initial biopsy and mandates biopsy after 6 weeks of three-drug chemotherapy.