Metanephric stromal tumor with unusual heterologous adipose differentiation: a case report and literature review.

A 10-year-old Thai boy with a metanephric stromal tumor (MST) with unusual adipose differentiation is reported. It has been described that the heterologous tissue element including fat is exceptionally demonstrated in MST cases. Multifocal grossly detected intratumoral adipose tissue as shown in this present case has not been elucidated and illustrated before. The presence of the fatty component may perhaps make it difficult in distinguishing the MST from its differential diagnoses such as Wilms tumor metanephric adenofibroma, mixed epithelial stromal tumor, and lipomatous renal tumors including angiomyolipoma. The recognition of this rare entity is important and can prevent the patients from complications and unnecessary treatment.