Metanephric stromal tumor
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Metanephric stromal tumor (MST) is a very rare, benign renal neoplasm that predominantly affect children.
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Metanephric stromal tumor is characterized by pure stromal morphology, hyper-differentiation, and no metastasis. The median age of diagnosis was 2 years. Less than fifty cases are reported in the literature, and only three of them are adult cases. More than half of all cases were diagnosed between six months and ten years after patients' first visits 1,2,3.
Patients typically present with asymptomatic abdominal mass. A few of them develop occasional hematuria, oliguria, or abdominal discomfort or pain 2.
The prevalence of BRAF V600E mutations in metanephric stromal tumor is in need of further investigation 3.
Metanephric stromal tumor is usually centered in the renal medulla except for one case in which the tumor is originated mainly from the renal cortex. Tumor size averages 5.7 cm (range 2.5- 12 cm) with a protruding white-cream, cystic-solid mass that is well-distinguished from normal renal tissue 3,4.
Ultrasound reveals a heterogenous mass that is isoechoic compared to the renal parenchyma. Color Doppler ultrasonography can help detect the displacement of the intrarenal vessels 2,4.
Contrast-enhanced abdominal computed-tomography shows a lobular mass with both cystic and solid components in the affected kidney. Computed-tomography angiography can also be used to detect extrarenal vasculopathy 2,5.
Treatment and prognosis
Surgery is the first-line treatment for metanephric stromal tumor. Nephrectomy, partial nephrectomy, and nephroureterectomy can also be indicated 2.
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- 2. Zhang X, Yadav P, Niu Q et al. Reevaluation of Metanephric Stromal Tumor Two Decades After It Was Named: A Narrative Review. J Pediatr Urol. 2020;16(6):822-9. doi:10.1016/j.jpurol.2020.08.011 - Pubmed
- 3. Marsden L, Jennings L, Gadd S, Yu M, Perlman E, Cajaiba M. BRAF Exon 15 Mutations in Pediatric Renal Stromal Tumors: Prevalence in Metanephric Stromal Tumors. Hum Pathol. 2017;60:32-6. doi:10.1016/j.humpath.2016.09.025 - Pubmed
- 4. Kacar A, Azili M, Cihan B, Demir H, Tiryaki H, Argani P. Metanephric Stromal Tumor: A Challenging Diagnostic Entity in Children. J Pediatr Surg. 2011;46(12):e7-e10. doi:10.1016/j.jpedsurg.2011.08.023 - Pubmed
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