Benign multicystic peritoneal mesothelioma mimicking recurrence of an ovarian borderline tumor: a case report

INTRODUCTION: Benign multicystic peritoneal mesothelioma is an extremely rare tumor that occurs mainly in women in their reproductive age. Its preoperative diagnosis and adequate treatment are quite difficult to attain. CASE PRESENTATION: Our patient was a 23-year-old Japanese woman who had a history of right oophorectomy and left ovarian cystectomy for an ovarian tumor at 20 years of age. The left ovarian tumor had been diagnosed on histology as a mucinous borderline tumor. Two years and nine months after the initial operation, multiple cysts were found in our patient. A laparotomy was performed and her uterus, left ovary, omentum and pelvic lymph nodes were removed due to suspicion of recurrence of the borderline tumor. A histological examination, however, revealed that the cysts were not a recurrence of the borderline tumor but rather benign multicystic peritoneal mesothelioma. There were no residual lesions and our patient was followed up with ultrasonography. She remains free from recurrence nine months after treatment. CONCLUSION: We report a case of benign multicystic peritoneal mesothelioma mimicking recurrence of an ovarian borderline tumor. Benign multicystic peritoneal mesothelioma should be suspected when a multicystic lesion is present in the pelvis as in the case presented here, especially in patients with previous abdominal surgery.