A 43-year-old woman received a hysterectomy with bilateral adnexectomy for a cystic tumor of the right broad ligament. The tumor, measuring 10 cm in diameter, was apart from the ovaries, oviducts, or uterus. The cyst wall had well-developed smooth muscle layers. Cells lining the cyst were benign-looking, relatively low columnar type, and were compatible with those of mesonephric origin. From the inner surface of the cyst numerous cauliflower-like structures projected into the lumen. These were predominantly papillary architecture covered by epithelial cells with occasional solid or glandular growth. Although structural and cellular atypism may suggest its malignant nature, the validity for frank malignancy of the present tumor could not be gained because of the absence of capsular invasion and metastasis. So, the diagnosis of papillary tumor of borderline malignancy was made. It may be safely assumed that the papillary tumor arose in a preexisting parovarian cyst of mesonephric origin.