Answer
The term rhabdoid is derived from the microscopic appearance of the tumor cells that resemble muscle cells. Rhabdoid tumors make up around 2% of renal neoplasms and are more common in infancy than in any other period. An association with brain tumors, especially medulloblastoma, has been described. The brain tumors may precede or appear several years after the detection of this tumor. Brain MRI is needed a part of the workup of rhabdoid tumors.
Like other neonatal masses, rhabdoid tumor of the kidney can be diagnosed in utero. In neonates, detection may follow their presentation with an abdominal mass, hypertension, or hypercalcemia. The age at presentation overlaps with that noted for congenital mesoblastic nephroma. The clinical and imaging characteristics of rhabdoid tumors of the kidney are similar to those of congenital mesoblastic nephroma, clear cell sarcoma, and Wilms tumor. Therefore, specific diagnosis is usually not possible. One important differentiating point is that clear cell sarcoma of the kidney and rhabdoid tumor of the kidney are invariably unilateral.
The prognosis for patients with a rhabdoid tumor of the kidney is much worse than that of patients with other renal tumors.
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This 6-year-old male child with hematuria was referred for a renal ultrasound scan. The scan shows a 6 x 8 cm solid mass at the lower pole of the right kidney displacing part of the collecting system in a cephalad direction. The mass is of uniform echogenicity with a vague small central hypoechoic area suggestive of tumor necrosis.
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Unenhanced axial CT scans shows a 6 x 8 cm mass low attenuation mass arising from the lower pole of the right kidney and extending into the anterior renal cortex. Also note subtle unrelated medullary left renal nephrocalcinosis.
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Enhanced axial CT scan shows a large solid tumor displacing a rim of functioning cortical tissue posteriorly. Note also a second small low attenuation mass in the functioning cortex.
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An IVU shows a nonfunctioning left kidney with a suggestion of ill-defined mass in the left loin due to a biopsy-proven Wilms tumor. Note the functioning right duplex renal collecting system. The chest radiograph in the same child shows a lung metastatic deposit (arrow). Images courtesy Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
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Axial US image shows a solid 4.5-cm solid mass anterior cortex, lower pole of the left kidney. Image courtesy of Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
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Sagittal US scan of the left kidney (same patient as in the previous image). Image courtesy of Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
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Axial and coronal reconstruction contrast-enhanced CT scan shows a fairly well defined left renal mass with a small central hypodense area due to central necrosis. Image courtesy Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
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Color Doppler US scan of the right kidney in a sagittal plane shows a 13-cm upper-pole, mainly solid tumor with a heterogeneous echo pattern displacing the functioning component of the kidney inferiorly.
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Color Doppler US scan of the right kidney in an axial plane shows a 13-cm upper-pole, mainly solid tumor with a heterogeneous echo pattern displacing the vessels and crossing the midline (same patient as in previous image). Images courtesy Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
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Unenhanced axial CT scans in the same patient as in the previous image shows a large, solid mass with a heterogeneous mass in the right renal fossa crossing the midline and displacing the liver anteriorly. Image courtesy of Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
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Contrast-enhanced axial CT scan in the same patient as in the previous images shows a large, solid mass with a heterogeneous mass with areas suggestive of necrosis. Note the normal functioning component of the right kidney. Image courtesy of Dr. Pedro Daltro and Dr. Edson Marchiori, Port Allegre, Brazil. edmarchiori@gmail.com
