[Borderline mixed epithelial tumor of the ovary]

One observation of borderline (proliferating) Brenner's tumour in combination with benign mucinous cystic adenoma is described. According to the International Histological Classification of the WHO (1977), such neoplasias are classified in the group of mixed epithelial tumours of the ovaries. In the great majority of the cases both epithelial components are morphologically mature, or mucinous cystic adenocarcinoma is combined with benign Brenner's tumour. In the reported case of mixed epithelial neoplasia of the ovaries malignancy occurred in the epithelial component of Brenner's tumour.