Primary retro peritoneal mucinous cystadenoma

Mucinous cystadenomas and cystadenocarcinomas of the ovary are clinically and histopathologically well-established common tumors. The retroperitoneal location of cystic tumors resembling ovarian mucinous cystadenoma and cystadenocarcinoma is rare. We report the clinical and pathological features of a rare retroperitoneal tumor in the presence of normal ovaries, primary retroperitoneal cystadenoma, and discuss the possible origin of retroperitoneal mucinous cystadenomas. A 39-year-old patient, gravida 3, parity 2, abortus 1, was admitted to the hospital with a lower abdominal pain. Physical examination revealed a left abdominal mass. Her pelvic examination was unremarkable. Laboratory evaluations including complete blood count, bleeding profile, urine analysis, chest X-ray and tumor markers (CEA, CA 125, CA 19.9 and CA 15.3) were within normal limits. A septated cystic lesion of 18 × 12 cm in the left abdominal quadrant was found by ultrasonography. The patient was taken to laparatomy and a retroperitoneal cystic lesion was found. The cystic lesion was extending from the kidneys to the lower left retroperitoneal area. On gross inspection the tumor was ovoid in shape, measuring 18 × 13 × 7 cm, with a smooth surface. The mass contained a mucinous appearing fluid; its walls were thin and it was not attached to any other structures. Both of the ovaries and the uterus were macroscopically normal. The cyst was shelled and removed totally with no spillage of the cystic fluid. A multilocular cyst filled with clear viscous fluid was seen on macroscopic evaluation. The internal surface was smooth. The wall of the cyst varied in thickness from 0.1 to 0.3 cm. Histologically the cyst wall was lined with a benign mucinous epithelium and a flat mesothelial-like lining was also found. The mucosal layer consisted of tall columnar cells with basal nuclei and eosinophilic cytoplasm (Fig. 1a). The outer layer of the cyst wall consisted of a thin layer of fibrous tissue. The increasing complexity of the cystic pattern (Fig. 1b) was due to multiple loculi. The cell boundaries of the epithelium were distinct and the microscopic appearance was benign. No separate ovarian tissue was identified in the cyst. The diagnosis was primary retroperitoneal mucinous cystadenoma. The postoperative course was uneventful and the patient was followed up for 14 months without recurrence. (a) Cyst wall showing a single layer of benign mucinous epithelium (hematoxylin–eosin, original magnification ×100). (b) Increasing complexity of the cystic pattern (hematoxylin–eosin, original magnification ×40). Tumors resembling ovarian mucinous cystadenomas and cystadenocarcinomas in the retroperitoneum are very unusual. The mucinous cystadenoma presented here is unique in its location in the retroperitoneum in the presence of normal ovaries. There are a few hypotheses considering their origin. One of the hypotheses is that they arise from ectopic ovarian tissue. Ectopic ovarian tissue is rarely present in other cases reviewed from the literature and there was no ovarian tissue in the pathologic specimens of our case. The results of special immunohistochemical stains and the absence of any ectopic ovarian tissue refutes the ectopic ovarian tissue hypothesis (1). There is also the possibility of it being derived from teratomas. Monodermal variants of teratomas are reported in this location (2). It is also possible that cysts may replace ectopic ovarian tissue or teratomas and mucinous epithelium may override all the other components. Another hypotheses is duplication of the intestine but this seems unlikely because enterogenic cysts are gut-like and they consist of one or two layers of smooth muscle, gut mucosa. The most widely accepted theory is coelomic metaplasia. Invagination of the peritoneum results in inclusion cysts and mesothelium of these cysts may undergo metaplasia resulting in cystadenomas (3). However, mesothelial cysts may result from ovulation or tuboovarian adhesions (4). The coelomic epithelium covering the cyst undergoes five distinct metaplasia processes (5): mucinous (endocervical), endometroid, serous (tubal), clear cell and squamous. Peritoneal mesothelium is the embryological equivalent of the ovarian surface epithelium. Metaplasia and neoplasia of this secondary mullerian system show the range of epithelium, which is found in ovarian epithelial tumors (6). Also in the pathogenesis of endometriosis coelomic metaplasia is proposed. Serous papillary tumors of the peritoneum in women are well documented, and serous cystadenocarcinomas of the retroperitoneum are also reported (6). Cystic mucinous tumors of the retroperitoneum may be benign, borderline or invasive as seen in ovarian tumors. The case presented here is a benign retroperitoneal cystadenoma. Histologically the cyst wall was lined by benign mucinous epithelium and a flat mesothelial-like lining suggesting the coelomic metaplasia. There was no ovarian tissue and no gut-like muscle in the pathologic specimens thus denying the ectopic ovarian tissue hypothesis and intestinal duplication in our case. Address for correspondence: Evrim Erdemoglu Kirkpinar sok. 12/4 Cinnah Cad. Çankaya 06690, Ankara Turkey e-mail: evrimmd@yahoo.com