Mixed epithelial and stromal tumour of the kidney: imaging features.

Objective: To describe the features on ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI) of mixed epithelial and stromal tumours of the kidney.
Patients and Methods: Five women with renal mixed epithelial and stromal tumours (mean age 55.6 years, range 49-59) who had preoperative imaging were retrospectively analysed. Three ultrasonograms, five contrast-enhanced CT scans, and one contrast-enhanced MRI examination were available for review. Specific imaging features analysed included lesion size, location, enhancement and cystic composition. The presence of calcification, septation, nodularity and a capsule were also evaluated.
Results: All mixed epithelial and stromal tumours appeared as well-marginated, multi-septate cystic masses with a nodular component. All lesions were classified as Bosniak category III (three) or IV (two). The presence of calcification (four) or a capsule (three) was variable. Two tumours invaginated into the renal pelvis with no invasion.
Conclusion: Mixed epithelial and stromal tumours of the kidney have a diverse radiographic appearance, indistinguishable from multilocular cystic nephroma and cystic renal cell carcinoma.