Mucinous cystadenoma of the sigmoid mesocolon: a previously unreported abdominal tumour

Abstract

A 24-year-old female presented with an 8-month history of vague left-sided abdominal pain, constipation and a feeling of abdominal distension. Clinical examination revealed a fixed smooth mass extending out of the left side of the pelvis. Ultrasound demonstrated a 20 cm x 15 cm cystic mass extending to the costal margin. The left ovary could not be identified separately from the mass and was the presumed source. Urgent laparoscopy, however, revealed normal ovaries and fallopian tubes. At laparotomy the cyst was seen to originate in the base of the sigmoid mesocolon. There was no attachment to, or shared blood supply with, any abdominal or pelvic organs. The cyst was completely removed by blunt dissection. The uterus, ovaries and fallopian tubes were normal and were not disturbed. The patient recovered uneventfully. Histological examination of sections of the cyst wall revealed an epithelium composed of columnar cells with basally placed nuclei and abundant mucin-producing cytoplasm (Fig. I). Underlying glands were present in the stroma, lmmunohistochemistry showed positivity for CAM 5.2 (Fig. 2) and CEA (epithelial markers) and negativity for Factor VIII (endothelial marker). These results indicate a tumour of epithelial origin, with the appearances of a mucinous cystadenoma. No evidence ofatypia or frank malignancy was seen. To our knowledge, this tumour has never been previously reported at this site. Retroperitoneal, mesenteric and omental cysts are rare abdominal tumours) occurring in approximately 1 in 105,000 hospitalized patients. 2 Retroperitoneal and mesenteric cysts can occur anywhere in the area between the duodenum and rectum, but are most common in the small bowel mesentery, especially the ileum. They are classified into developmental, neoplastic, traumatic and infectious, according to their origin. ~5 Most cases are either developmental cysts of lymphatic or enteric derivation (lymphangioma, enteric duplication cysts) or cystic neoplasms, such as teratomas and mesotheliomas. A rare group of urogenital cysts are derived from vestigial remnants of the embryonic urogenital apparatus, s Mesenteric cysts are frequently misdiagnosed pre-operatively, 6 or are found only incidentally at operation for other conditions. Gross appearance does not allow accurate differentiation of the lesions. 7 Presentation is usually with abdominal distension or a palpable abdominal mass, however, pain, vomiting, diarrhoea, and symptoms of gastrointestinal and urinary obstruction have all been reported) There is no definitive diagnostic test. However, ultrasound, computerized topography and magnetic resonance imaging may be of assistance in determining the source and relationships of any cyst. Occasionally, barium studies and an