Recurrent Metanephric Stromal Tumor in an Infant

Reevaluation of metanephric stromal tumor two decades after it was named: A narrative review

OBJECTIVE

The aim of this narrative review is to provide an overview and update of metanephric stromal tumor (MST).

MATERIALS AND METHODS

All English language studies published from January 1, 2000 to December 31, 2019 in PubMed, EBSCO, Elsevier ScienceDirect, Springer Link and Taylor & Francis databases were searched with the search terms "metanephric stromal tumor" for this review.

RESULTS

Seventeen eligible case reports representing 47 patients according to inclusion and exclusion criteria were included in this study. The average age of the patients was under 4 years (range from 2 d to 56 y) and over half of the cases (52.1%, 25/47) are were diagnosed as MST by accident or during examinations for other diseases. Morphologically, tumor specimens of almost all cases presented concentric "onion-skin cuffing" or characteristic collarettes around renal tubules under low power. There were 79.2% (18/25) of patients exhibited BRAF V600E mutations. Immunohistochemistry (IHC) is characterized by CD34 (+), Vimentin (+), Desmin (-), S-100 (-), SMA (-). Most patients underwent surgeries, and no metastasis or recurrence was found except for one case.

CONCLUSION

MST is a rare benign pediatric renal tumor with surgical treatment as the first choice. CT examinations and ultrasonography are two widely accepted techniques for the diagnosis of MST. Percutaneous renal biopsy (PRB) is an effective and accurate way of preoperative diagnosis, however, it is not recommended for children under 10 years or with a cystic mass in CT images. The relationship between BRAF V600E mutations and mild clinical manifestations of MST is in need of further verification by biological experiments and clinical studies.

Paediatric metanephric tumours: a clinicopathological and molecular characterisation

To characterize metanephric tumours in children, we performed a literature review investigating paediatric metanephric adenomas (MA), metanephric stromal tumours (MST) and metanephric adenofibromas (MAF). Including two patients from our own institution (MA, MAF), 110 individual cases (41 MA, 20 MAF, 49 MST) were identified. Additionally, fifteen composite tumours were identified, with areas of MA/MAF and Wilms tumour (WT) or papillary carcinoma. No distinct clinical or radiological features could be defined. In pure metanephric tumours, histologically proven distant metastases were reported once (MA), relapse was reported once (MST) and one tumour-related death occurred (MST). Somatic BRAF-V600E mutations were tested in 15 cases, and identified in 3/6 MA, 3/3 MAF, and 6/6 MST. In our institution the MA harboured a somatic KRAS-G12R mutation. Overall, paediatric metanephric tumours are difficult to discriminate from other renal tumours at presentation, behave relatively benign, and the occurrence of composite tumours warrants analysis of underlying (genetic) pathways.

An approach to renal masses in pediatrics

Renal masses in children may be discovered during routine clinical examination or incidentally during the course of diagnostic or therapeutic procedures for other causes. Renal cancers are rare in the pediatric population and include a spectrum of pathologies that may challenge the clinician in choosing the optimal treatment. Correct identification of the lesion may be difficult, and the appropriate surgical procedure is paramount for lesions suspected to be malignant. The purpose of this article is to provide a comprehensive overview regarding the spectrum of renal tumors in the pediatric population, both benign and malignant, and their surgical management.

Metanephric stromal tumor: An unusual pediatric renal neoplasm

A renal tumor in a 14-month- old child, who was initially diagnosed as mesoblastic nephroma, but on review post surgery was diagnosed as hyper-differentiated metanephric stromal tumor, with its excellent prognostic outcome. An attempt is made to document imaging features that may enable one to suspect this rare condition. The literature is reviewed with emphasis on its distinction from its look-alikes in the pediatric age group.

Metanephric stromal tumor: a challenging diagnostic entity in children

A case with a renal mass diagnosed as metanephric stromal tumor is presented. A 6-year-old boy presented with frequently recurring urinary tract infections. He had been followed up at different medical centers for the last 2 years with a 2 × 2 cm simple cyst localized in the inferior pole of the left kidney. At our center, ultrasonography revealed a heterogeneous mass in the left kidney with a central cystic component. The patient underwent operation for left renal mass, and heminephrectomy was performed. The 5 × 4 × 2.5 cm left heminephrectomy specimen showed a partially cystic mass composed of bland spindle cells distributed haphazardly, entrapping tubules and glomeruli and producing fine collarettes around some tubules. The cysts were lined with a 1-layered flat or cuboidal epithelium. Histopathologically, the tumor was diagnosed as metanephric stromal tumor. Metanephric stromal tumor is a rare renal neoplasm of childhood that can present as a cystic mass, and the solid component can go radiologically undetected because of the blurring infiltrative margins. By presenting this rare entity, the authors suggest that this should be included in the differential diagnosis, thereby helping to avoid complications and unnecessary treatment.