AB089. The diagnosis and therapy of mixed epithelial and stromal tumor of the kidney

Objective: To explore the clinical and pathological features of mixed epithelial and stromal tumor of the kidney (MESTK).

Methods: Clinical and pathological characteristics of two cases of MESTK were studied.

Results: Two cases of MESTK which occurred in a 56-year-old male and 35-year-old female uncommonly. Radiology of two cases both consisted of an irregular mixture of solid and cystic areas. The cysts were multilocular with smooth walls and low-density cystic liquid. Tumors were diagnosed as Bosniak III and IV. Solid parts presented a mild-to-moderate enhancement and delayed enhancement without any enhancement of the cystic ones. Clinic features presented with a large cystic/solid mass in the right renal region without a history of estrogen/progestogen treatment and other case in the left renal. Microscopically, the tumor was composed of a mixture of stromal and epithelial components. Immunohistochemical staining revealed that the epithelial components were positive for AE1 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 S-100, and alpha-inhibin. One case had radical nephrectomy and the other had NSS. Twelve months after resection, the patients were well without evidence of recurrence.

Conclusions: MESTK is a rare clinical entity. It is generally considered to be the hypothesis that proliferation of remnants of the primitive mesenchyme in the kidney in situation of sex-steroid abnormity. MESTK is a benign tumor with good prognosis, but there is malignant potential. It is very difficult to different diagnose before operation, MESTK should be considered as a possible diagnosis in cases of cystic renal mass, especially in peri-menopausal women or those who have received hormonal therapy. In the general, the therapy of MESTK is NSS.

Keywords: Kidney; mixed epithelial and stromal tumor