Mixed epithelial and stromal tumour of the kidney.

Mixed epithelial and stromal tumour (MESTK) of the kidney is a rare and benign tumour composed of epithelial and spindle cell stromal components with solid and cystic architecture. MESTK is most commonly seen in perimenopausal women, especially those on long-term oestrogen therapy. MESTK is often asymptomatic, detected incidentally on imaging studies. Diagnosis is established by histological examination. Microscopy is reminiscent of ovarian stroma. Malignant transformation, metastasis and recurrences are extremely rare. Treatment is surgical excision of the tumour with usually no recurrences after surgery and good prognosis. We describe a case of MESTK found incidentally on imaging studies. 2015 BMJ Publishing Group Ltd.