Neoplasms of the peritoneum

Carcinoma peritonei is a common terminal event in many cases of carcinoma of the stomach, colon, ovary or other abdominal organs and also of the breast and bronchus. The peritoneum, both parietal and visceral, is studded with secondary growths, and the penitoneal cavity becomes filled with clear, straw-coloured or blood-stained ascitic fluid.

The main forms of penitoneal metastases are:

  discrete nodules by far the most common variety;

  plaques varying in size and colour;

  diffuse adhesions this form occurs at a late stage of the disease, and gives rise, sometimes, to a ‘frozen pelvis

Gravity probably determines the distribution of free malignant cells within the penitoneal cavity. Cells not caught in penitoneal folds along the attachments of mesenteries gravitate into the pelvic pouches or into a hernial sac, enlargement of which is occasionally the first indication of the condition. Implantation occurs also on the greater omentum, the appendices epiploicae and the inferior surface of the diaphragm. It is remarkable how often patients riddled with intraperitoneal carcinoma preserve their nutrition and look and feel comparatively well until the terminal stage.

Differential diagnosis

Early discrete tubercles common in tuberculous peritonitis are greyish and translucent and closely resemble the discrete nodules of penitoneal carcinomatosis, but the latter feel hard when rolled between the finger and thumb, making the differential diagnosis tolerably simple. Fat necrosis usually can be distinguished from a carcinomatous nodule by its opacity. Penitoneal hydatids can also simulate malignant disease after rupture of a hydatid cyst, with seeding of daughter cysts.

Treatment

Ascites due to carcinomatosis of the peritoneum may respond to systemic chemotherapy. In other cases intrapenitoneal chemotherapy with cisplatin, mitomycin C or methotrexate after drainage of ascites may be effective.

Tamoxifen (an oestrogen receptor site competitor) can dramatically reduce ascites due to breast cancers which are oestrogen dependent.

Pseudomyxoma peritonei

This rare condition occurs more frequently in females. The abdomen is filled with a yellow jelly, large quantities of which are often more or less encysted. The condition is associated with both mucinous cystic tumours of the ovary and appendix. Recent studies suggest that most cases arise from a primary appendiceal tumour with secondary implantation on to one or both ovaries. It is often painless and there is frequently no impairment of general health for a long time. Although an abdomen distended with what seems to be fluid that cannot be made to shift should raise the possibility, the diagnosis is more often suggested by ultrasound and CT scanning or made at operation. At laparotomy masses of jelly are scooped out. The appendix, if present, should be excised together with any ovarian tumour. Unfortunately recurrence is usual. Pseudomyxoma peritonei is locally malignant but does not give rise to extraperitoneal metastases. Occasionally the condition responds to radioactive isotopes or intraperitoneal chemotherapy which may be used in recurrent cases.

Mesothelioma

As in the pleural cavity, this is a highly malignant tumour. Asbestos is a recognised cause. It has a predilection for the pelvic peritoneum, but it is not radiosensitive. Alkylating agents have given remissions. Benign forms are reported. Recent regimens of multiple chemocytotoxic agents have been reported as curative for early forms of malignant mesothelioma.

Desmoid

This is considered under familial adenomatous polyposis (Chapter 57).