Primary retroperitoneal cystic mucinous borderline tumour mimicking an ovarian neoplasm: a case report and literature review

Primary cystic mucinous tumours of the retroperitoneum are rare tumours and cases with borderline pathology are even rarer. Approximately 33 cases of cystadenomas, 35 cases of cystadenocarcinoma and nine cases of borderline malignancy have been published in the literature to date. These tumours have been described exclusively in females; however, very rarely, they have been described in male patients [4, 5].

The histogenesis of these tumours is not clear and several theories have been proposed. Most authors suggest mucinous metaplasia in pre-existing mesothelium-lined cysts, which are more common in this location. Invaginations of peritoneum/mesothelium result in these inclusion cysts that undergo mucinous metaplasia, thus, resulting in a mucinous cystadenoma [1, 3, 6]. Some have suggested that clusters of coelomic epithelial cells could be deposited along the route of ovarian descent and, by proliferation or metaplastic differentiation, develop into these cystic tumours [7, 8]. Other theories include an origin from ectopic ovarian tissue and teratomas [9].

The differential diagnosis includes metastatic mucinous tumours, from sites such as ovaries, the intestines, including the appendix and pancreas [9]. Other neoplastic lesions in this site include cystic lymphangioma, cystic teratoma, cystic mesothelioma, mullerian cyst, epidermoid cyst and tailgut cyst [2].

The three main categories of cystic mucinous tumours of the retroperitoneum are reviewed with regards to clinical presentation and diagnostic histological appearances, together with treatment options and survival data.

The majority of patients in the three groups of mucinous tumours (benign, borderline and malignant) have been asymptomatic, some presented with vague symptoms of abdominal fullness and, rarely, others presented as an abdominal mass. Most reports have included information regarding the uterus, tubes and ovaries being normal [3, 4, 12, 13].

There are limitations in the role of pre-operative radiological imaging; a final diagnosis can only be made after histological examination and the exclusion of a mucinous tumour elsewhere in the abdomen by careful clinical and radiological examination.

Regarding treatment, there is agreement on complete surgical excision of the lesion. The role of additional surgery and how extensive it should be is not clear when the uterus and ovaries are macroscopically normal.

For malignant lesions, some authors have recommended more aggressive treatment. Hysterectomy with bilateral salpingo-oophorectomy performed simultaneously or later may be necessary to improve survival [6, 9]. Omentectomy and pelvic/para-aortic lymph node resection were also performed in a few cases [1, 6]. However, Kessler et al. suggest that an extensive surgical procedure with serious consequences cannot be justified when the uterus and ovaries are macroscopically normal, and also when follow up in the majority of the reported cases is deficient. The only reason for this procedure to be performed is in post-menopausal women or patients who have completed child-bearing [23]. More conservative surgery has been proposed by Law et al., who advocate for laparoscopic excision of the tumour and complete evaluation of the abdominal and pelvic organs, sparing fertility in these women [24]. Adjuvant chemotherapy is not a standard treatment and its effectiveness is uncertain [13]. It is suggested that it is beneficial in cases with spillage of cyst fluid associated with tumour rupture during surgical intervention [1] or when the invasion of adjacent structures is macroscopically evident [4].

In borderline lesions, there is no clear evidence about the additional removal of the uterus, tubes and ovaries or about post-operative chemotherapy. The literature suggests that prognosis in these cases is good and complete surgical excision appears to be curative (Table 1). The prevention of cyst fluid spillage during surgical manipulation is important [20].

Bearing in mind the differential diagnosis of primary retroperitoneal mucinous tumours, it will allow appropriate pre-operative planning, enabling the surgeon to consider an extra-peritoneal surgical approach and remove the cyst in toto (without any spillage) with intact peritoneum possible.

Biological behaviour can be better defined and survival data can be collected as more cases are reported. Our case is another addition to the literature on this rare tumour with borderline pathology, which was treated by tumour excision without additional therapy, and has been disease-free in the 12 months of follow up, until now.

From the available evidence, we feel that the experience of retroperitoneal mucinous tumours remains limited and minimal data exists to define the appropriate management. In view of the rarity and possible malignant potential of these lesions, we are of the opinion that an early diagnosis and treatment with multi-disciplinary review is essential. Further follow up should be individualised and is dependent on factors like peri-operative spillage and tumour load.