OBJECTIVE To study the clinicopathological features of mixed epithelial and stromal tumor of the kidney(MESTK). METHODS Clinical and pathological characteristics of one case of MESTK was studied. RESULTS A case of MESTK which uncommonly occurred in a 16-year old adolescent male presented with dysuria and a large mass in the right renal region without a history of estrogen/progestogen treatment and/or obesity or urogenital surgery. Radiology revealed a large cystic/solid mass within the right kidney. Grossly, it was well demarcated and had a solid and cystic appearance on sectioning. Microscopically, the tumor was composed of a mixture of stromal and epithelial components. The epithelial component was composed of flat to columnar cells forming glands or tubules. The stromal components essentially consisted of bland, loosely packed spindle cells in an edematous and myxoid background. In some areas, there were smooth muscle cells forming bands and fascicles but no ovarian-type stroma was present. Immunohistochemical staining revealed that the epithelial components were positive for AE1/AE3 and focally positive for estrogen receptor (ER),progesterone receptor(PR), CD10 and Vimentin, whereas the stromal components were positive for ER, PR, Desmin and smooth muscle actin(SMA). Both epithelial and stromal components were negative for HMB-45, S-100, alpha-inhibin and WT-T. Five months after resection, the patient was well without evidence of recurrence. CONCLUSION; MESTK occurred in a pubertal male, as in the current case, supports the hypothesis that proliferation of remnants of the primitive mesenchyme in the kidney in situation of sex-steroid abnormity may play an important role in the pathogenesis of male MESTK.