A 44-year-old female with no remarkable medical history was admitted to hospital complaining of abdominal distention and a growing palpable mass for more than a year. On physical examination, a smooth football-sized mass was palpable in the left lower quadrant with mild tenderness. Abdominal ultrasonography and contrast-enhanced CT showed a large cystic mass with solid components. Further consultation on CT results indicated the presence of an enhanced mural nodule of 4.6x1.5 cm and an enhanced thick irregular wall of 6 mm (Figure 2). Consequently, an imaging diagnosis of retroperitoneal cystadenocarcinoma was made. Laboratory findings were within normal limits. Laparoscopic surgery was then performed, revealing an oval-shaped high-tension cyst located in the left retroperitoneal space, pushing inwards on the descending and sigmoid colons. After effortless separation from adjacent tissues, 1000 mL of muddy brown liquid was drained through a puncture hole of 0.3 cm, followed by careful suture of the cyst wall. The huge mass was then completely removed; a specimen retrieval bag was used to retrieve the tumour. However, since the initial decompression of the mass was not protected by the retrieval bag, although no gross spillage of fluid content was visible, the possibility of intraperitoneal micrometastasis could not be ruled out.
On gross examination, the tumour was 20 cm in diameter and was not connected to the left ovary. The cyst had a thick and rough wall with mural nodules of different sizes and solid components. Microscopically, mucinous and papillary glands with focal areas of haemorrhage and interstitial fibrosis were present. There was mild to moderate epithelial atypia with areas of intraepithelial carcinoma represented by severe nuclear atypia. Immunohistochemistry exam showed diffuse positive staining for CK 7 and CEA, as well as focal positive staining for CK 20 (Figure 3). Considering the retroperitoneal location of the mass, the tumour was therefore diagnosed as bPRMC with intraepithelial carcinoma.
The patient's recovery was uneventful, and she was discharged on the fifth post-operative day. Although no further treatment was given, post-operative gastroscopy, colonoscopy, and positron emission tomography/computed tomography (PET/CT) were conducted to rule out metastatic disease. The patient had no evidence of disease 2 months after surgery.