Paratubal borderline serous tumor in a postmenopausal woman: a case report

Unlike borderline ovarian tumors, paratubal borderline tumors are extremely rare gynecologic tumors. They occur in reproductive-aged females at an earlier stage of disease and have a good prognosis. A 61-year-old woman, gravida 3 para 3, presented with progression of ovarian cyst. Computed tomography revealed a 6-cm simple cystic lesion without enhancing papillary projections. The patient underwent total laparoscopic hysterectomy and bilateral salpingo-oophorectomy. Frozen specimens showed that the tumor was benign, thereby confirming a final diagnosis of paratubal borderline serous tumor. The patient refused comprehensive surgical staging and opted for close follow-up. The patient remains asymptomatic with no evidence of recurrence at the 24-month follow-up. To the best of our knowledge, this is the first reported case of paratubal borderline serous tumor in a postmenopausal patient. The findings of this study and those of other case reports can contribute to the understanding, diagnosis, treatment and prognosis of these rare tumors.


Introduction
In asymptomatic postmenopausal women, most adnexal cysts are benign and simple cysts with a prevalence of 15%-20%. Of these, paratubal cysts have a prevalence of 5% [1,2]. Most cysts are asymptomatic and are found incidentally during pelvic surgery [3]. To date, nine cases of primary paratubal borderline tumors (PBTs) have been reported in reproductive-aged patients, of which seven were paratubal borderline serous tumors, one was a borderline mucinous tumor and one was a borderline endometroid tumor [3][4][5]. Here we present the eighth case of paratubal borderline serous tumor to be reported in the literature and the first to be reported in a postmenopausal woman. PBT is similar to ovarian cancer in histological appearance; however, its clinical course and prognosis are not well understood owing to its rarity. As there is currently no standard treatment for PBTs, treatment needs to be individualized.
Fertility-sparing surgery should be considered in patients who wish to have children in the future and long-term follow-up is necessary to detect recurrence [3,5]. In postmenopausal women, treatment has been extrapolated according to the guidelines for ovarian tumors, indicating that comprehensive surgical staging surgery may be preferred [6]. However, as there have been no reports of metastasis and positive lymph nodes in PBTs, it remains debatable whether comprehensive surgical staging surgery should be performed.

Patient and observation
A 61-year-old woman, gravida 3 para 3, presented with an increased size of ovarian cyst. Her history revealed a diagnosis of left ovarian cyst 3cm in diameter 3 years previously. Her serum cancer antigen (CA) 125 and CA 19-9 levels were within the normal ranges, and she was followed up at 6-month intervals at a private hospital.
The ovarian cyst size had not changed in size and structure on biannual transvaginal ultrasound (TVS). However, she was referred to our institution in July 2016 with progression of ovarian cyst to 6cm on a pelvic ultrasonogram 2 weeks ago. The patient underwent menopause at the age of 48 years, with an uneventful past menstrual cycle. She had no medical history except the benign thyroid nodule, no relevant surgical history and had not received hormonal therapy.
Routine blood chemistry and serum tumor marker analysis showed that the levels of carcinoembryonic antigen, CA 19-9, CA 125, and human epididymis protein 4 were all within the normal ranges. Uterine cervical cytology at the time of admission was normal. TVS showed a left ovarian unilocular cyst, size 6cm × 5cm × 4cm, with diffuse lowlevel internal echoes, thin walled, smooth margined, no septa and no papillary projections (Figure 1). The uterus size was 6cm × 4cm × 3cm, and a 1cm uterine myoma was found in the fundus. Pelvic

Discussion
Paratubal cysts are common disorders, representing approximately 10% of all adnexal masses [1,7]. In asymptomatic postmenopausal women, the prevalence of adnexal cysts and paratubal cyst is reported to be 15% to 20% and 5%, respectively [2] and most adnexal cysts are benign and simple cysts. Unlike borderline ovarian tumors that account for 5% to 20% of all epithelial ovarian cancer, PBTs are extremely rare and are reported as case reports. Borderline tumors are identified by epithelial proliferation with no stromal invasion [8].
A MEDLINE search using the search terms "paratubal cyst, borderline tumor, low malignancy potential, and atypical proliferative tumors" PBTs is similar to ovarian cancer in histological appearance, but its clinical course and prognosis are not well understood [7,8]. Most PBT cases have been reported to occur in reproductive-aged women, with an age range of 17-61 years with an earlier stage of disease [3]. In postpubertal years, an increase in the size of the paratubal cyst is observed due to the secretory activity of epithelium and the influence of hormonal activity [13]. Of previously reported cases, four of the ten presented with pelvic pain, two had menstrual abnormalities and four had asymptomatic adnexal cysts. Furthermore, of the ten patients, tumors were located on the right side in seven patients and on the left side in three patients. All tumors were unilateral, measuring 3-19cm in diameter. Tumors size appeared to be inversely proportional to the patient's age, with adolescent patients exhibiting larger sizes. Nine of the ten PBTs were described as unilocular and one was multilocular.
Four patients underwent laparoscopic surgery. Various types of surgery were conducted depending on the patient's age, preference, and fertility preservation. All patients undergoing surgical staging were diagnosed using the FIGO staging of disease and showed a good prognosis without recurrence at follow-up periods.
Nine of ten PBTs were described as having papillary projections on the image modalities or intraoperative findings, but only the present case showed no papillary projections. There were no cases of elevated serum CA 125 level in the ten cases and three of the eight frozen biopsy results were misdiagnosed as benign cysts. TVS is the most useful diagnostic tool to assess the risk of malignancy in adnexal masses and shows the high sensitivity but relatively low specificity in the diagnosis of paratubal cysts [1,14]. While the risk of malignancy in unilocular adnexal cysts in postmenopausal women is low, some cases have reported contrasting conclusions [1], as measurement of serum CA125 did not significantly increase the diagnostic accuracy of

Competing interests
The author declare no competing interests.

Authors' contributions
JongChul Baek wrote the paper and prepared figures; JongChul Baek reviewed drafts of the paper. The author has read and agreed to the final manuscript.