Abstract
Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare benign kidney tumor. In rare cases, malignant transformation, such as sarcomatoid features indicates poor clinical outcomes. In this study, we will describe a 45 years old man with a diagnosis of MESTK with malignant transformation of the sarcomatoid component, after right radical nephrectomy. The patient underwent chemotherapy with adriamycin, ifosfamide, and granulocyte-colony stimulating factor (G-CSF). The radiological characteristics of MESTK can pose diagnostic challenges due to its non-unique radiological appearance. The presence of sarcomatoid transformation is a hallmark feature of malignant MESTK which can be very aggressive.