Gynaecological Pathology

Background: Brenner tumours of the ovary are rare and account for 1%-3% of all ovarian tumours.They can occur in isolation or be associated with other ovarian neoplasms such as mucinous cystadenomas and teratomas.They typically present as unilateral solid ovarian masses and predominantly cystic forms are rare.We present a case of a benign Brenner tumour that is predominantly cystic in appearance.Case report: The patient was a 55-year-old female who presented with a large left ovarian cyst.On histopathological examination, the left ovary was replaced by a thin-walled cyst lined by bland transitional-type epithelium with an overlying layer of bland mucinous cells, and no solid areas were present.The cyst wall was fibrotic with underlying luteinised ovarian stroma.The findings were those of a cystic benign Brenner tumour with stromal luteinisation.Discussion: Brenner tumours of the ovary are often incidental findings and are easily diagnosable in their typical solid form.When cystic change is prominent, as in our case, the typical transitional cells may be obscured, making diagnosis challenging.It is important to recognize Brenner tumour as one of the differential diagnoses when evaluation an ovarian cyst, and judicious use of immunohistochemistry can be helpful in making the diagnosis.