Year : 2009 | Volume
: 52 | Issue : 3 | Page : 389--391
Metanephric stromal tumor: A novel pediatric renal neoplasm
V Rajalakshmi, Philip Chandran, Selvambigai, Jai Ganesh
Department of Pathology and Pediatric Surgery, ICH and HSPL for Children (Madras Medical College), Chennai - 8, Tamil Nadu, India
22/2, Murrays gate road, Alwarpet, Chennai, Tamil Nadu - 600 018
Metanephric stromal tumor of kidney is a novel pediatric benign stromal specific renal neoplasm. A few cases have been reported in adults also. This tumor is usually centered in the renal medulla with a characteristic microscopic appearance which differentiates this lesion from congenital mesoblastic nephroma and clear cell sarcoma of the kidney. In most cases complete excision alone is curative. The differentiation of metanephric stromal tumor from clear cell sarcoma of the kidney will spare the child from the ill effects of adjuvant chemotherapy. In this communication we describe the gross and microscopic features of metanephric stromal tumor in a one-month-old child with good prognosis.
|How to cite this article:|
Rajalakshmi V, Chandran P, Selvambigai, Ganesh J. Metanephric stromal tumor: A novel pediatric renal neoplasm.Indian J Pathol Microbiol 2009;52:389-391
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Rajalakshmi V, Chandran P, Selvambigai, Ganesh J. Metanephric stromal tumor: A novel pediatric renal neoplasm. Indian J Pathol Microbiol [serial online] 2009 [cited 2020 Aug 15 ];52:389-391
Available from: http://www.ijpmonline.org/text.asp?2009/52/3/389/55003
Stromal tumors of the kidney form 15% of the pediatric renal tumors. Metanephric stromal tumor (MST), a purely stromal specific renal neoplasm has a characteristic microscopic appearance that helps to differentiate between congenital mesoblastic nephroma (CMN) and clear cell sarcoma of kidney (CCSK). Complete excision is curative in most cases of MST. The differentiation of MST from clear cell sarcoma of the kidney is very important as it will spare the child from the adjuvant chemotherapy.
A one-month-old female child presented with abdominal swelling. Ultrasonogram revealed a solid and cystic mass in the left kidney. Intravenous voiding ureterogram of the right kidney was normal. No excretion was seen in left kidney. Diagnosis of Wilm's tumor of the left kidney was made and left nephrectomy was done. Histopathological sections from the nephrectomy specimen showed features of MST with immunohistochemistry (IHC) findings confirming the diagnosis.
Gross: Nephrectomy specimen showed kidney measuring 6 x 4.4 cm. In one pole of the kidney a solid and cystic lesion of 3 x 3 cm centered in the renal medulla filled with necrotic material was seen. The wall of the cyst showed tiny papillary projections in a few foci with tan areas.
Microscopy under low power revealed renal parenchyma with a neoplasm having a nodular appearance and showing scalloped borders with renal parenchyma [Figure 1] and [Figure 2]. The neoplasm showed cystic areas [Figure 3].
There was perivascular and peritubular cuffing by the neoplastic cells forming collarettes with onionskin appearance [Figure 4]. The neoplastic cells were spindle-shaped with hyperchromatic nuclei. Blood vessels with tortuosity and hypertrophied media with epithelioid transformation of medial cells were seen [Figure 5]. No heterologous differentiation was seen.
IHC for CD 34 was positive focally and negative for Desmin.
Based on the microscopic appearance and IHC a diagnosis of MST was made.
MST is an under-reported pediatric pure stromal neoplasm of kidney with good prognosis. A few cases have been reported in adults also. MST along with metanephric adenofibroma and metanephric adenoma represent a spectrum of well-differentiated nephroblastic lesions that appear to be related to Wilm's tumor.  Argani and Beckwith  reported 31 cases of MST in their series with a benign course. In most cases complete excision alone is curative. The differentiation of MST from CCSK will spare the child from the toxic ill effects of adjuvant chemotherapy.
MST is usually a lesion centered in the renal medulla, but in one case continuous extension through the bladder to the prostatic urethra has been reported.  Microscopically, this neoplasm is an unencapsulated spindle to stellate cell lesion that entraps native kidney. Under low power it has a nodular appearance. Onion skin cuffing (collarettes) around tubules and blood vessels in myxoid background are also seen. These collarettes and angiodysplasia of intra tumoral vessels are the distinctive features of MST. Glia and cartilage-heterologous differentiation was seen in a few cases in the series of Argani and Beckwith. Our case did not show heterologous differentiation. Twelve of the 13 cases tested in the Argani and Beckwith series showed CD 34 positivity, and it was patchy in six of their cases as in our case. CD 34 positivity of MST differentiates it from CCSK. Desmin was negative in all these cases differentiating it from CMN.  Desmin was negative in our case also.
CCSK and CMN have to be differentiated from MST.
MST is differentiated from CCSK by the characteristic branching capillary vascular pattern seen in CCSK which is absent in MST. Nuclei in MST are thin and hyperchromatic and nuclei are ovoid and clear in CCSK. CD 34 can be a helpful differentiating feature because CCSKs are uniformly negative for this stain.
MST is differentiated from CMN by scalloped borders in contrast to the deeply invasive nature of CMN.
Nodular low power pattern of MST is in contrast to the sharply defined linear transitions. Heterologous differentiation and vascular changes are specific to MST though cartilage is occasionally seen in CMN. Desmin is negative in MST and it is positive in CMN. Desmin was negative in our case also.
All the MSTs behaved clinically in a benign fashion hence it is important to differentiate MST from aggressive mimics as excision or nephrectomy alone seems to be curative.
In conclusion, this communication highlights a case of MST, an under-reported pediatric renal neoplasm with good prognosis after total excision.
We thank Miss. Preeti Pathanjali, for her secretarial services in the preparation of the manuscript and Dr. Priyadarshini, Post Graduate.
|1||Argani P, Beckwith JB, Renal neoplasms of childhood. In: Stacy. E Mills, editor. Sternberg's Diagnostic surgical pathology. 4 th ed. Lippincot Williams and Wilkins: Philadelphia; 2004. p. 2029-30.|
|2||Argani P, Beckwith JB. Metanephric stromal tumor: Report of 31 cases of a distinctive pediatric renal neoplasm. Am J Surg Pathol 2000;24:917- 26.|
|3||Lorenzo AJ, Timmons C, Weinberg A, Megison SM, Snodgrass WT. Metanephric stromal tumor with urothelial extension. J Urol 2003;169:1095- 7.|
|4||Nadasdy T, Roth J, Johnson DL, Bane BL, Weinberg A, Verani R, et al . Congenital Mesoblastic nephroma an immunohistochemical and lectin study. Hum Pathol 1993;24:413-9.|