DOI: 10.1148/rg.246045040
RadioGraphics 2004;24:1709-1713
© RSNA, 2004
Best Cases from the AFIP
Anaplastic Wilms Tumor: Radiologic and Pathologic Findings1
Thomas M. Aquisto, MD,
Robert Yost, MD and
Kelley W. Marshall, MD
1 From the Department of Radiology, Emory University Hospital, Atlanta, Ga (T.M.A.); and the Departments of Pathology (R.Y.) and Radiology (K.W.M.), Children’s Healthcare of Atlanta at Scottish Rite. Received March 15, 2004; revision requested April 14 and received June 25; accepted July 27. All authors have no financial relationships to disclose. Address correspondence to T.M.A., 211 E Ohio St, Unit 1514, Chicago, IL 60611 (e-mail: taquisto@yahoo.com).
Index Terms: Kidney neoplasms, 81.326 • Kidney neoplasms, diagnosis, 81.326 • Kidney neoplasms, in infants and children, 81.326
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History
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An 8-year-old girl developed progressive right upper quadrant abdominal pain and vomiting over several days, with decreasing activity and appetite. She was taken to the emergency room for evaluation; concerns were that she might have appendicitis.
At examination, she was afebrile with stable vital signs, and abdominal examination results were remarkable for a palpable and tender right upper quadrant mass 4 cm below the right costal margin. Laboratory results were normal except for a mildly elevated white blood cell count and urinalysis findings of 3+ ketones, with 4 red blood cells per high-power field and 2 white blood cells per high-power field.
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Imaging Findings
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Computed tomography (CT) of the abdomen and pelvis demonstrated a large, right-sided mass originating from the lower pole of the right kidney that extended into the subcapsular and perinephric space (Fig 1). The mass was heterogeneous in attenuation but predominantly solid, containing regions of low attenuation suggesting hemorrhage or necrosis. Delayed imaging demonstrated no definite continuity of the mass with the collecting system. Distortion of the collecting system was noted secondary to local mass effect and accompanying mild pelvicaliectasis. Overall, the mass measured 9 cm (anteroposterior) x 6.5 cm (mediolateral) x 8 cm (craniocaudal). There was normal enhancement of the right renal artery and vein as well as normal enhancement of the inferior vena cava (IVC).
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Figure 1a. (a) Axial contrast material-enhanced CT image obtained through the abdomen shows a large, lobulated, heterogeneously attenuating mass of the posterolateral right kidney with involvement of the subcapsular and perinephric spaces. The areas of lower attenuation suggest the presence of hemorrhage and necrosis. (b, c) Sequential axial CT images from the same data acquisition as a show distortion of the renal collecting system from mass effect without definite invasion. There is normal enhancement of the inferior vena cava (IVC).
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Figure 1b. (a) Axial contrast material-enhanced CT image obtained through the abdomen shows a large, lobulated, heterogeneously attenuating mass of the posterolateral right kidney with involvement of the subcapsular and perinephric spaces. The areas of lower attenuation suggest the presence of hemorrhage and necrosis. (b, c) Sequential axial CT images from the same data acquisition as a show distortion of the renal collecting system from mass effect without definite invasion. There is normal enhancement of the inferior vena cava (IVC).
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Figure 1c. (a) Axial contrast material-enhanced CT image obtained through the abdomen shows a large, lobulated, heterogeneously attenuating mass of the posterolateral right kidney with involvement of the subcapsular and perinephric spaces. The areas of lower attenuation suggest the presence of hemorrhage and necrosis. (b, c) Sequential axial CT images from the same data acquisition as a show distortion of the renal collecting system from mass effect without definite invasion. There is normal enhancement of the inferior vena cava (IVC).
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On the basis of these findings, the impression was that the renal mass likely represented a Wilms tumor. There was no lymphadenopathy and no renal vein or IVC thrombosis.
Ultrasound (US) images (obtained for guided biopsy) demonstrated a large, lobulated, somewhat circumscribed lesion, with heterogeneous echotexture but overall slightly hyperechoic (Fig 2), in the posterior inferior pole of the right kidney with scattered heterogeneous internal echoes, consistent with the CT findings. The images were obtained for needle biopsy of the lesion.
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Figure 2. Sagittal static US image obtained through the inferior right kidney shows the large, predominantly hyperechoic mass, which is located in the posteroinferior part of the kidney and contains areas of heterogeneous echotexture.
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Pathologic Evaluation
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The patient underwent right radical nephrectomy. Gross pathologic analysis demonstrated a bulky mass protruding from the inferoposterior aspect of the kidney (Fig 3). The viable tumor tissue was composed of pale pink, friable, and focally hemorrhagic tissue. The tumor occupied the posteroinferior aspect of the kidney and infiltrated the adjacent retroperitoneal and perirenal soft tissue. The mass measured approximately 4.0 x 4.0 x 3.0 cm. The upper half of the kidney was unremarkable. The renal pelvis was of normal width and hilar vessels were unremarkable, with no evidence of renal pelvis or hilar vascular invasion. The gross appearance of the adrenal gland was normal.
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Figure 3. Photograph of the gross specimen from right radical nephrectomy shows the large mass extending from the posterior aspect of the kidney. The tumor tissue is pink and friable and extends into the adjacent retroperitoneal soft tissue. There is no evidence of invasion of the renal pelvis or hilar vessels.
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Microscopic sections through the right kidney mass showed a neoplastic small round blue cell tumor composed predominantly of blastemal and epithelial tubular elements (Fig 4a). The neoplastic cells were oval to irregular in shape and were hyperchromatic with occasional prominent nucleoli. Pleomorphism was present with occasional anaplastic cells noted that had large, irregularly shaped hyperchromatic nuclei. Abundant mitoses and apoptotic figures were noted throughout the lesion (Fig 4b). The tumor extended into venous structures. Tumor cells were not seen in the collecting system or ureter. Sections through the adrenal gland were normal. Small islands of tumor were noted within and beyond a thin fibrous tumor capsule as well as extending into the perinephric fat (Fig 4c).
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Figure 4a. (a) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) of a section through the mass shows multiple neoplastic cells, which are oval to irregular in shape and have hyperchromatic nuclei. The tumor cells are composed predominantly of blastemal and tubular elements. (b) Photomicrograph obtained at a higher power (original magnification, x200; hematoxylin-eosin stain) shows areas of abundant mitoses and apoptotic figures, findings consistent with anaplasia. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a different section through the mass shows small islands of tumor tissue within and beyond a thin fibrous tumor capsule.
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Figure 4b. (a) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) of a section through the mass shows multiple neoplastic cells, which are oval to irregular in shape and have hyperchromatic nuclei. The tumor cells are composed predominantly of blastemal and tubular elements. (b) Photomicrograph obtained at a higher power (original magnification, x200; hematoxylin-eosin stain) shows areas of abundant mitoses and apoptotic figures, findings consistent with anaplasia. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a different section through the mass shows small islands of tumor tissue within and beyond a thin fibrous tumor capsule.
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Figure 4c. (a) Photomicrograph (original magnification, x100; hematoxylin-eosin stain) of a section through the mass shows multiple neoplastic cells, which are oval to irregular in shape and have hyperchromatic nuclei. The tumor cells are composed predominantly of blastemal and tubular elements. (b) Photomicrograph obtained at a higher power (original magnification, x200; hematoxylin-eosin stain) shows areas of abundant mitoses and apoptotic figures, findings consistent with anaplasia. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a different section through the mass shows small islands of tumor tissue within and beyond a thin fibrous tumor capsule.
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The final diagnosis was Wilms tumor with diffuse anaplasia.
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Discussion
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Wilms tumor is the most common abdominal malignancy of childhood. Wilms tumor usually manifests as an asymptomatic abdominal mass but may manifest with abdominal pain, particularly when there is intratumoral hemorrhage (1,2). Most cases develop in otherwise normal children; however, approximately 1% of the time they can be familial. In familial cases, extrarenal anomalies occur in up to 7%–8% of cases, which include overgrowth syndromes (such as Beckwith-Wiedemann syndrome and congenital hemihypertrophy) as well as an association with sporadic aniridia, genital malformations, and other chromosomal malformations (WAGR syndrome [Wilms tumor associated with aniridia, genital abnormalities, and retardation]). Syndromes associated with Wilms tumor include Perlman syndrome (fetal gigantism with multiple congenital abnormalities), Bloom syndrome, Drash syndrome (male pseudohermaphroditism and nephritis), trisomy 18, and linear sebaceous nevus syndrome. Wilms tumor occurs bilaterally approximately 10% of the time, and when it occurs in this fashion there are more frequently associated extrarenal findings such as those mentioned earlier. The mean age at presentation is 3 years old. Invasion of the renal vein or IVC is not uncommon and is important for surgical planning, including those thrombi that extend directly into the right atrium. Pulmonary metastatic disease can occur in up to 20% of cases, including recurrent Wilms tumor and late metastases (3).
Histologically, Wilms tumor is characterized by a largely diverse cell population. The classic triphasic pattern is present in the tumor when it contains blastemal, stromal, and epithelial elements; however, these cell types occur in varying proportions with some consisting of only biphasic or monophasic patterns (1,4). It is important to distinguish tumors with unfavorable histologic findings that are associated with tumor recurrence and death. These unfavorable histologic features occur in approximately 10% of patients but account for almost 50% of tumor-related deaths (4). Tumors that have a more favorable histologic composition do not contain any anaplastic changes. Anaplasia, the presence of gigantic polyploid nuclei within the tumor sample, is a feature that is associated with a high resistance to chemotherapy and a poor prognosis, especially if it is diffuse (4,5). Anaplastic tumors typically manifest at a later age, have more association with abdominal pain at the time of presentation, and have a higher frequency of associated chromosomal abnormalities (2,4,6).
Typical US findings are a large, well-defined mass originating from the kidney, usually increased in echogenicity but often heterogeneous secondary to accompanying hemorrhage or calcification. Doppler US is excellent in evaluating the presence and extent of renal vein and IVC tumor thrombus (1,3). At CT, Wilms tumor typically appears as a large, spherical intrarenal mass that enhances to a lesser degree than the remaining normal renal parenchyma. Areas of heterogeneous attenuation can be present secondary to hemorrhage, calcification, or fat (1,3). At magnetic resonance (MR) imaging, Wilms tumor is generally isointense to renal parenchyma on T1-weighted images and hyperintense on T2-weighted images. After intravenous administration of gadolinium contrast material, Wilms tumor demonstrates enhancement but to a lesser degree than that of normal renal parenchyma (1,7).
When evaluating cross-sectional images in the setting of suspected Wilms tumor, it is important to check for lymph node involvement, liver and lung metastases, and involvement of the contralateral kidney by a synchronous Wilms tumor and to evaluate the anatomic distribution of the renal vein and IVC and the relationship of the mass to the ureters and pelvicaliceal system.
Another important issue in evaluating a renal mass, especially one that extends into the suprarenal fossa, is determining whether the mass truly arises from the kidney. If it is determined that the mass is suprarenal in location, the mass then likely represents an adrenal neoplasm such as neuroblastoma, pheochromocytoma, or some other primary adrenal neoplasm. Neuroblastoma tends to occur in slightly younger children (<2 years), is often calcified (85% at CT), and has a tendency to surround vessels but does not usually invade them. Adrenal neoplasms manifesting in an older child may have associated biochemical activity to help distinguish them. It can be difficult at times to distinguish a renal mass from a suprarenal mass. Wilms tumor tends to grow more like a "ball," displacing vessels and often demonstrating vascular invasion. Wilms tumor is less likely to calcify (15% at CT) and when it does is more likely to have curvilinear calcifications (3). MR imaging can be helpful due to its multiplanar capabilities in cases that are difficult or equivocal at CT (7).
Other renal tumors in the differential diagnosis of a pediatric renal mass include multilocular cystic nephroma, which can be difficult to distinguish from Wilms tumor but is often seen as a fluid-filled cystic mass with multiple thin septa. Mesoblastic nephroma has a similar appearance to Wilms tumor but is usually differentiated by patient age, as it occurs in the first few months of life. Other less common pediatric renal tumors include clear cell sarcoma, which has a tendency to metastasize to bone (unlike Wilms tumor), and rhabdoid tumor (3).
Treatment of Wilms tumor is dependent on the local tumor burden as well as the detection of distant metastases and tumor histology. Tumor stage is based solely on anatomic findings at surgery per the National Wilms Tumor Study (NWTS) and is classified as intrarenal disease (stage I), local extrarenal extension including venous invasion (stage II), advanced local disease including nonhematogenous tumor confined to the abdomen (stage III), hematogenous metastatic disease (stage IV), or bilateral disease (stage V) (8,9). The combination of histologic tumor grade with surgical anatomic staging determines treatment. In general, the more favorable the histologic findings (ie, no evidence of anaplasia) and the more confined the disease extent (ie, stage I), the more favorable the prognosis. Anaplasia in itself does not necessarily indicate a grave prognosis, especially if it is focal and if diagnosed in stage I, and in fact this subgroup of patients can have an excellent prognosis. However, diffuse anaplasia with more advanced staging usually indicates a very poor prognosis.
Preoperative chemotherapy can be used for treatment as well as radiation therapy. Radiation therapy is generally used for anaplastic tumors, as well as tumors that have a favorable histologic composition with distant metastases (8,10). Both radical nephrectomy and kidney-sparing surgery are used, especially in bilateral involvement (11).
Unfortunately, the outcome in our patient’s case was the same as in most cases of diffuse anaplastic Wilms tumor. After diagnosis, the child received seven of eight courses of chemotherapy including whole abdominal irradiation and underwent surgery, which consisted of a right nephrectomy. Surveillance US during the seventh course of chemotherapy revealed several large metastatic lesions in the liver and retroperitoneum. She passed away a few weeks later.
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Footnotes
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Abbreviations: IVC = inferior vena cava
Editor’s Note.—Everyone who has taken the course in radiologic pathology at the Armed Forces Institute of Pathology (AFIP) remembers bringing beautifully illustrated cases for accession to the Institute. In recent years, the staff of the Department of Radiologic Pathology has judged the "best cases" by organ system, and recognition is given to the winners on the last day of the class. With each issue of RadioGraphics, one or more of these cases are published, written by the winning resident. Radiologic-pathologic correlation is emphasized, and the causes of the imaging signs of various diseases are illustrated.
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References
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- Feinstein K. Renal neoplasms. In: Kuhn J, Slovis T, Haller J, eds. Caffey’s pediatric diagnostic imaging. 10th ed. Philadelphia, Pa: Elsevier, 2004; 1788-1790.
- Davidoff AM, Soutter AD, Shochat SJ. Wilms tumor presenting with abdominal pain: a special subgroup of patients. Ann Surg Oncol 1998; 5:213-215.[Abstract]
- Donnelly LF. Genitourinary tract. Fundamentals of pediatric radiology. Philadelphia, Pa: Saunders, 2001; 158-159.
- Beckwith JB. New developments in the pathology of Wilms tumor. Cancer Invest 1997; 15:153-162.[Medline]
- Re GG, Willingham MC, el Bahtimi R, Brownlee NA, Hazen-Martin DJ, Garvin AJ. Anaplasia and drug selection-independent overexpression of the multidrug resistance gene, MDR1, in Wilms’ tumor. Mod Pathol 1997; 10:129-136.[Medline]
- Peres EM, Savasan S, Cushing B, Abella S, Mohamed AN. Chromosome analyses of 16 cases of Wilms tumor: different pattern in unfavorable histology. Cancer Genet Cytogenet 2004; 148:66-70.[CrossRef][Medline]
- Meyer JS, Harty MP, Khademian Z. Imaging of neuroblastoma and Wilms’ tumor. Magn Reson Imaging Clin N Am 2002; 10:275-302.[CrossRef][Medline]
- Ritchey ML. Wilms’ tumor. In: Belman AB, King LR, Kramer SA, eds. Clinical pediatric urology. 4th ed. London, England: Dunitz, 2002; 1271-1275.
- Gow KW, Roberts IF, Jamieson DH, Bray H, Magee JF, Murphy JJ. Local staging of Wilms’ tumor: computerized tomography correlation with histological findings. J Pediatr Surg 2000; 35:677-679.[CrossRef][Medline]
- Kalapurakal JA, Dome JS, Perlman EJ, et al. Management of Wilms’ tumour: current practice and future goals. Lancet Oncol 2004; 5:37-46.[CrossRef][Medline]
- Paya K, Horcher E, Lawrenz K, Rebhandl W, Zoubek A. Bilateral Wilms’ tumor: surgical aspects. Eur J Pediatr Surg 2001; 11:99-104.[CrossRef][Medline]
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History
Imaging Findings
