International Journal of Clinical and Diagnostic Pathology

Mixed epithelial and stromal tumor (MEST) represents a recently described biphasic kidney neoplasm, which predominantly affects perimenopausal females. We describe case of a 35 year male patient with a MEST. Computed tomography (CT scan) showed an expansive lesion affecting the right kidney. Grossly, Greyish-white, a solid-cystic tumor was identified, which measured 3x 3 cm. On microscopic examination, a biphasic tumor constituted by stromal and epithelial elements, without significant Atypias, was identified. The stromal element was composed of spindle cells revealing positive immunoexpression for SMA (α-Smooth Muscle Actin) and CD10. The epithelial component exhibited a predominantly tubular pattern showing positive immunoreaction for PAX8. The diagnosis of MEST was then established.