A nurse is caring for a pediatric client who is suspected to have Wilms tumor.
Which of the following diagnostic procedures is key in confirming the diagnosis of Wilms tumor?

Choice A rationale

Biopsy of the tumor is the definitive diagnostic procedure for Wilms tumor. This involves the surgical removal of a tissue sample from the suspected mass, which is then examined microscopically by a pathologist. Histopathological analysis confirms the presence of malignant cells characteristic of nephroblastoma, differentiating it from other renal masses and guiding subsequent treatment protocols. Normal renal tissue structure is preserved in healthy kidneys.

Choice B rationale

Bone marrow aspiration is primarily used to diagnose hematological malignancies or assess for metastatic disease in certain cancers. While Wilms tumor can metastasize, particularly to the lungs, bone marrow involvement is uncommon and not the primary diagnostic method for confirming the initial diagnosis of the tumor itself. Normal bone marrow contains hematopoietic stem cells and a balanced cellularity.

Choice C rationale

A CT scan of the abdomen and chest provides detailed anatomical information about the tumor's size, location, and extent of involvement within the kidney and surrounding structures, as well as checking for metastasis to the lungs. While crucial for staging and surgical planning, a CT scan is an imaging modality and does not provide a definitive tissue diagnosis. Normal abdominal organs appear with distinct densities.

Choice D rationale

Abdominal ultrasonography is often the initial imaging modality used to evaluate a suspected abdominal mass in children due to its non-invasive nature and lack of radiation exposure. It can identify the presence of a renal mass and distinguish between solid and cystic lesions, but like CT, it cannot definitively diagnose Wilms tumor without tissue sampling. Normal kidneys appear as solid, homogeneous organs.