Mixed Epithelial and Stromal Tumor of the Kidney: Clinicopathologic Features and Surgical Outcomes in Four Patients

Mixed epithelial and stromal tumor (MEST) is a rare neoplasm of the kidney that is seen mostly in middle-aged women with a history of hormonal contraceptive consumption. Mixed epithelial and stromal tumors are usually benign tumors with minimal chances of metastasis and recurrence. However, few malignant transformations of MEST have been recorded. In perimenopausal patients presenting with a complex cystic renal mass in the renal system with a history of selective estrogen receptor modulator (SERM) therapy, MEST must be a differential diagnosis. The key treatment in MEST is surgical resection of the tumor. A MEST is similar to adult cystic nephroma (ACN), but MEST has complex epithelial and stromal components. We present a case series of four patients with a characteristic tumor of the kidney with the presence of mixed epithelial and stromal components. The ages of the patients ranged from 48 years to 55 years (mean age being 51 years). One of these cases is relatively rare as the patient is male and has no history of taking hormonal medications. Patients underwent surgical removal of tumors, and all of the patients recovered well postoperatively.