A 38-year-old, gravida 4, para 2, female Korean patient presenting with indigestion and vague abdominal discomfort of several months' duration was referred from a private clinic for a large retroperitoneal mass that was discovered on abdomen computer tomography. She had suffered from cervical tuberculosis 7 years ago, and this had been confirmed by excisional biopsy at a private clinic, and it was eradicated after a 1 year treatment with anti-tuberculosis medications. The large cystic abdominal mass was palpated on her right flank and in the RLQ abdomen on the physical examination. It was mobile, non-tender and estimated to be about 8 cm in diameter. The rest of her pelvic examination was unremarkable. The laboratory findings including colonoscopy and serum tumor markers (CEA, CA 125, and CA 19-9) were within the normal limits. Imaging studies on abdomen and pelvis computer tomography showed an unilocular cystic mass, 10x8x6 cm3 in dimensions, was located at the inferior aspect of the liver and posterior along the right colon, and the right retroperitoneal mass had displaced the right colon ventromedially. It was an encapsulated cystic mass that contained fluids, and there was no lesion in the pelvic organs (Figure 1).
A celiotomy was performed; there was a large cystic retroperitoneal mass adhered to the right colon and its mesocolon, right kidney and duodenum, but it had not invaded to the adjacent organs. Macroscopically there was no lesion observed in the ovaries and fallopian tubes, appendix, right colon, kidneys and pancreas. The retroperitoneal tumor was completely removed with no spillage of its contents, and no combined resection with the associated organs was performed.
Upon gross examination, the specimen was a thin-walled, multilocular cyst with a dominant loculus that measured 10.0x7.5x5.5 cm3. The external surface is smooth and pinkish. Upon opening it, it contained mucinous fluids and inner surface is smooth. The wall of the cyst contained smaller cysts; the largest of these measured 0.8 cm in diameter. The thickness of the walls was less than 0.1 cm. There are no solid areas or papillary projections. On the histologic examination, the cyst was lined by a single layer of tall columnar epithelium with clear cytoplasm and small nuclei that were basely located in the cells (Figure 2). There was no papillary growth or stromal invasion of epithelium. The cyst wall consisted of fibrocollagenous tissue of varying cellularity and vascularity. No pancreatic or ovarian components were found (Figure 3). Immunohistochemical staining showed that the lining cells were positive for cytokeratin, cytokeratin 7, CAM 5.2, and carcinoembryogenic antigen, but the cells were negative for cytokeratin 19, epithelial membrane antigen, estrogen and progesterone (Figure 4).
The final diagnosis was primary mucinous cystadenoma arising from the retroperitoneum. The patient had an uneventful postoperative recovery, and there was no lesion or recurrence on the follow-up abdomen and pelvis computer tomography at postoperative one year.