Quantitative Perfusion Analysis of Contrast-enhanced Ultrasound Might Help Differentiate Benign and Malignant Solid Cystic Lesions of the Kidney: A Case Report and Literature Review

Background: Mixed epithelial and stromal tumor of the kidney (MESTK) is a rare benign lesion that appears as a solid cystic renal lesion or complex renal cystic lesion on medical imaging. There are no definite imaging criteria for METSK diagnosis. Case Presentation: We present a case of a solid cystic renal mass that was evaluated by contrast-enhanced ultrasound (CEUS) during an imaging workup. The patient underwent nephrectomy and histopathological confirmation of MESTK. The lesions showed hypoenhancement during the process. Quantitative perfusion analysis showed the septation of the solid cystic lesion to have lower peak enhancement with a longer rise time compared to the normal renal cortex. Discussion: CEUS can visualize the microcirculation of the organ and reconstruction of the vessels. By providing a more detailed visualization of the microvessel, CEUS is a useful tool for further characterizing renal lesions that show indeterminate enhancement on CT. This study determined the time to peak to be shorter for the cancerous lesion than the normal renal cortex, while peak intensity did not differ between the cancerous lesion and the normal renal cortex. Conclusion: Quantitative perfusion analysis of CEUS may be useful for differentiating benign and malignant solid cystic renal masses. Further investigation is needed to determine whether peak intensity is a useful parameter in differentiating benign and malignant solid cystic lesions of the kidney. © 2024 The Author(s).