We report a case of a 24-year-old female who underwent laparoscopy for a presumed benign ovarian mass. Frozen sections at laparoscopy initially revealed a borderline papillary serous ovarian tumour. Final histology showed an invasive papillary serous ovarian tumor (grade 1). Subsequent staging laparotomy conducted 13 days later revealed peritoneal implantations thus upgrading the initially thought Stage Ia papillary serous ovarian tumour at laparoscopy to Stage IIc. The patient after laparotomy had an uneventful postoperative course and received six cycles of chemotherapy based on taxol and carboplatin. A short review of the literature is also presented, concerning the factors which affect the patient's prognosis in cases of unexpected ovarian malignancy found during laparoscopy that are treated with subsequent staging laparotomy.