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Year : 2018  |  Volume : 1  |  Issue : 2  |  Page : 87-89

Metanephric adenofibroma in a child with impaired renal function

Department of Pediatric Surgery, Hospital Militar Central, Affiliated Universidad Militar Nueva Granada Medical School, Bogota D.C, Colombia

Date of Web Publication27-Dec-2018

Correspondence Address:
Dr Juliana Mancera
Department of Pediatric Surgery, Hospital Militar Central, Transversal 3° No 49 - 00 Piso 8., Bogota 110231
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/AJPN.AJPN_27_18

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A 5-year-old girl presented with a history of bilateral reflux nephropathy and a left kidney mass, suspicious of Wilms tumor on imaging studies. She underwent radical nephrectomy according to the National Wilms Tumor Study protocol. The pathology report was consistent with metanephric adenofibroma (MAF), for which radical nephrectomy was considered curative. MAF is a benign, uncommon tumor, which is frequently confused with Wilms tumor on diagnostic imaging; histopathologic studies reveal the diagnosis. The diagnostic and management approach to MAF is discussed.

Keywords: Pediatric, kidney neoplasms, nephrectomy, Wilms tumor

How to cite this article:
Mancera J, Chacón D, Luengas JP. Metanephric adenofibroma in a child with impaired renal function. Asian J Pediatr Nephrol 2018;1:87-9

How to cite this URL:
Mancera J, Chacón D, Luengas JP. Metanephric adenofibroma in a child with impaired renal function. Asian J Pediatr Nephrol [serial online] 2018 [cited 2021 Sep 19];1:87-9. Available from: https://www.ajpn-online.org/text.asp?2018/1/2/87/248640

  Introduction Top

Metanephric adenofibroma (MAF) is a benign, uncommon, tumor with epithelial and stromal cellularity, which is frequently confused with a Wilms tumor. Only pathologic studies reveal its exact histologic pattern. We present a patient with MAF and history of bilateral reflux nephropathy with limited renal function. The purpose of this report is to discuss the diagnostic and management approach to MAF.

  Case Report Top

We present a 5 years old girl with history of bilateral reflux nephropathy due to Grade IV and II vesicoureteral reflux in the right and left kidney, respectively. Following bilateral ureteric reimplantation at the age of 3 years, she had an estimated glomerular filtration rate (eGFR) of 55 ml/min/1.73 m2 at presentation at age of 5 years. During nephrology review, an ultrasound was performed that incidentally showed a hypoechoic lesion on the left kidney. Abdominal computed tomography (CT) confirmed that the left kidney was enlarged with a nodular, hypodense, and noncystic mass in its middle and lower third area [Figure 1]a, measuring approximately 46 mm × 43 mm, with heterogeneous enhancement [Figure 1]b. There was no vascular infiltration or lung metastasis. The patient underwent radical nephrectomy without complications. Surgical findings were of a hypertrophic left kidney with an external purplish surface and normal perirenal fat. The tumor was resected with free margins. The specimen was cut through its main axis, revealing a whitish, swirling tumor of 4.5 cm × 4.2 cm × 3.8 cm in the inferior and medial pole of the kidney, in close contact with renal calyces [Figure 1]c and d]. On the first postoperative day, the patient received chemotherapy with actinomycin D, according to the National Wilms Tumor Study (NWTS) protocol. She had an uneventful recovery.
Figure 1: Investigations. Abdominal computed tomography revealed a (a) Left renal mass in the lower pole (arrow) (b) Hypodense mass in the lower half of the left kidney (arrow), which, in the (c and d) Operative specimen showed heterogeneous enhancement

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Histo pathology indicated a mixed epithelial – stromal tumor, with capsule and hilum free of tumor. It was a nonencapsulated, nodular lesion, comprised of stroma in zones of cells [Figure 2]a with uniform nuclei, that formed rings around tubules that were lined by an epithelium without atypia [Figure 2]b. Extensive intratumor angiodysplasia with chondroblast focal differentiation was detected. In a few zones, the fibroblastic stroma grew in an intracanalicular form. There was no anaplasia, necrosis, or mitosis. Immunohistochemistry was positive for vimentin [Figure 2]c, indicating mesenchymal origin, focally positive for Wilms tumor-1 (WT-1) in the stromal nodules [Figure 2]d, and positive for the epithelial marker Ber-EP4 in the epithelial ducts [Figure 2]e. The study was negative for myogenin, a marker for rhabdomyosarcoma [Figure 2]f. Ki67, a specific nuclear marker for cell proliferation, was positive in 7%–10% tumor cells. Retroperitoneal nodes were negative for tumor infiltration. According to these findings, the tumor was consistent with MAF. Hence, the surgery and oncology teams decided to follow-up the patient with no additional chemotherapy. The patient's current GFR is 73.3 ml/min/1.73 m2.
Figure 2: HIstopathology. (a) Stroma containing zones of cells with uniform nuclei (b) Tubular epithelium without atypia. Immunohistochemistry (c) positive for vimentin, (d) focally positive for WT-1, (e) positive for Ber-EP4, and (f) negative for myogenin

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  Discussion Top

MAF is a rare renal tumor, with less than ten cases reported in the pediatric ages group.[1] It corresponds to a mixed tumor with epithelial and stromal cellularity, being the least frequent of the metanephric neoplasias. These are a spectrum of histologically benign lesions that come from the metanephric blastema.[2],[3],[4],[5],[6]

MAF presents chiefly in either infancy or puberty, on average between 6 and 10 years of age, with a male to female ratio of 2:1.[1],[7],[8] No risk factors or urogenital diseases have been described to be associated with this entity. It can present with hematuria, hypertension, and polycythemia;[9] and can enlarge considerably to present as a palpable abdominal mass, indistinguishable from other pediatric solid abdominal tumors.[5] Its radiologic appearance is difficult to differentiate from the relatively more common Wilms tumor, which accounts for 85% of the primary renal tumors in childhood.[6],[7],[10] MAF has no specific radiologic findings that allow it to be suspected it preoperatively.

The diagnosis of this tumor depends on pathology and immunohistochemistry on operative specimen.[2] The histologic appearance of MAF is variable: it has a biphasic composition of spindle cells of mesenchymal origin and inactive embryonic epithelial components. On immunohistochemistry, positivity for WT-1, vimentin, and pair box gene 2 indicates stromal elements, while that for AE1/AE3 (anti-cytokeratin monoclonal antibodies), S100, pair box gene 8, CK8/18, and epithelial membrane antigen) denotes epithelial elements.[7] This neoplasm behaves as a hypermature and differentiated form of Wilms tumor[1],[2],[9] analogous to the neuroblastoma spectrum.[9] While the distinction between MAF and Wilms tumor is fundamental in the diagnostic process to avoid exposing the patient to toxic chemotherapy, they share some histologic characteristics such as being biphasic, the presence of cells of mesenchymal origin and embryonic epithelium nodules.[8],[10]

Regarding treatment, no standard treatment protocol has been described. However, since MAF is a benign tumor, a simple nephrectomy is curative. Partial nephrectomy is not considered, because there are no imaging findings that define the biologic behavior of tumors, and consequently, a less aggressive treatment, in consideration of a probable Wilms tumor.[3],[7] In addition, these neoplasms have a potential malignant demeanor as aggressive multifocal components such as renal papillary carcinoma (28%), and Wilms tumor (20%) can exist within the mass.[1] Radical nephrectomy is curative in some of these neoplasms.[5]

In the present case, a radical nephrectomy was performed in consideration of Wilms tumor. We followed the guidelines of NWTS protocol to manage this type of cancer, thus biopsy before the resection was not indicated given the risk of changing the tumor stage of the disease and the requirement of adjuvant therapy. In this patient's context, the radical nephrectomy was curative, being the best option to avoid the renal deterioration, optimize the rate of healing, and decrease the percentage of relapse. This proceeding was justified in the benign etiology of the mass, free tumor margins, and no evidence of blastema in pathology report.

This case had an excellent clinical course after nephrectomy and the previously deteriorated kidney has shown stable renal function after the radical nephrectomy.

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Conflicts of interest

There are no conflicts of interest.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

  References Top

Chami R, Yin M, Marrano P, Teerapakpinyo C, Shuangshoti S, Thorner PS, et al. BRAF mutations in pediatric metanephric tumors. Hum Pathol 2015;46:1153-61.  Back to cited text no. 1
Galluzzo ML, Garcia de Davila MT, Vujanić GM. A composite renal tumor: Metanephric adenofibroma, Wilms tumor, and renal cell carcinoma: A missing link? Pediatr Dev Pathol 2012;15:65-70.  Back to cited text no. 2
Arroyo MR, Green DM, Perlman EJ, Beckwith JB, Argani P. The spectrum of metanephric adenofibroma and related lesions: Clinicopathologic study of 25 cases from the National Wilms Tumor Study Group Pathology Center. Am J Surg Pathol 2001;25:433-44.  Back to cited text no. 3
Picken MM, Curry JL, Lindgren V, Clark JI, Eble JN. Metanephric adenosarcoma in a young adult: Morphologic, immunophenotypic, ultrastructural, and fluorescence in situ hybridization analyses: A case report and review of the literature. Am J Surg Pathol 2001;25:1451-7.  Back to cited text no. 4
Raj P, Khanolkar A, Sarin YK. Metanephric adenofibroma masquerading as Wilms' tumor. APSP J Case Rep 2016;7:37.  Back to cited text no. 5
Yang F, Zhang C, Wang M, Tian X, Wang W, Xing N, et al. Metanephric adenofibroma in a young adult. Int Braz J Urol 2017;43:563-5.  Back to cited text no. 6
Yao DW, Qu F, Hu SW, Zheng JY, Wang JM, Zhu XY, et al. Metanephric adenofibroma in a 10-year-old boy: Report of a case and review of the literature. Int J Clin Exp Pathol 2015;8:3250-6.  Back to cited text no. 7
Turner Ii RM, Tomaszewski JJ, Fox JA, Galambos C, Cannon GM Jr. Metanephric adenofibroma. Can J Urol 2013;20:6737-8.  Back to cited text no. 8
Argani P. Metanephric neoplasms: The hyperdifferentiated, benign end of the Wilms tumor spectrum? Clin Lab Med 2005;25:379-92.  Back to cited text no. 9
Shek TW, Luk IS, Peh WC, Chan KL, Chan GC. Metanephric adenofibroma: Report of a case and review of the literature. Am J Surg Pathol 1999;23:727-33.  Back to cited text no. 10


  [Figure 1], [Figure 2]


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