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).