ECR 2002 COD #5: Cystic peritoneal mesothelioma

Clinical symptoms had begun 2 years previously with swelling on the right side of the abdomen without other symptoms. Laboratory data showed anaemia. The tuberculin reaction was positive. Chest films were considered normal. Abdominal CT demonstrated ascites, without other relevant findings. Abdominal laparoscopy revealed only multiple adhesions. The patient was treated with antituberculous drugs, but there was no clinical improvement. Ultrasonography and CT were performed.

CPM occurs mainly in women, with a reported mean age at presentation of 37 years [2]. Common presenting features include abdominal pain and distension, usually associated with a pelvic or abdominal mass. Although CPM is most frequently seen in the pelvis, it may affect any peritoneal or omental surface. Furthermore, abdominal presentation of the neoplasm is thought to be secondary to extension from the pelvis.

On ultrasonography (US) the typical appearance of CPM is a non-specific multiloculated anechoic cystic mass. CT allows evaluation of the nature and extension of the tumour. The differential diagnosis of CPM includes malignant peritoneal mesothelioma, abdominal lymphangioma, pseudomyxoma peritonei and tuberculous peritonitis [3]. Malignant peritoneal mesothelioma presents as a nodular thickening of the peritoneum, associated with abdominal soft tissue masses and invasion of intestinal walls. A cystic appearance is not expected.

Abdominal lymphangioma occurs in children and young adults, with a retroperitoneal, mesenteric or omental location. Pelvic involvement is uncommon. Demonstration of fat tissue within the neoplasm may help to diagnose lymphangioma.

Pseudomyxoma peritonei is considered to be a complication of a mucin-producing neoplasm, appearing as solid masses producing peritoneal implants and visceral parenchymal involvement.

On CT, tuberculous peritonitis is suggested when a smooth peritoneum with minimal thickening is found in association with macronodules and pronounced enhancement. The masses often show low-density central areas and calcifications.

The therapeutic approach in patients with cystic abdominal or pelvic masses depends on the type of tumour. Therefore, a preoperative diagnosis is important. Aspiration cytology may be useful and the aspirate from a CPM contains mesothelial cells showing a focal brush border [4], instead of a tendency to form clusters and aggregates, as occurs in conditions such as viral infections, cirrhosis or connective tissue disorders with mesothelial hyperplasia. At surgery the tumour consists of multiple watery cysts forming a confluent mass. Due to its tendency to recur after surgery, the level of malignancy of CPM is considered to be intermediate between benign and malignant mesotheliomas [5]. Invasion of abdominal structures has not been reported and cystic mesothelioma has no metastatic potential.

Treatment of CPM consists of surgical excision. Adherence may make a complete removal of the neoplasm difficult. In these cases, marsupialisation of the remaining cysts is recommended. Radiotherapy and chemotherapy are of no value in this neoplasm [4]. The prognosis of CPM is good. Further resection is usually required due to the tendency of this tumour to recur (27-50%) [2].