Light micrograph of a serous borderline tumour which is a non-invasive, low-grade epithelial neoplasm of the ovary. It was previously known as serous ovarian tumour of low malignant potential. It has a papillary architecture consisting of finger-like structures lined by somewhat uniform tumour cells. A small percentage of women with this tumour go on to develop serous carcinoma, usually low-grade, but sometimes high-grade. Haematoxylin and eosin stained section. Magnification: x200 when printed at 10 centimetres wide.