Peritoneal mesothelioma with an unusual gross appearance (a case report).
Primary malignant tumours of the pericardium, pleura and peritoneum are rare. These tumours are typically characterized by serosal spread and shallow invasion into parenchymatous organs., The peritoneal mesotheliomas are less common than those of the pleura., We came across a case of primary peritoneal mesothelioma with an unusual gross appearance of multiple cysts resembling hydatid cysts. This case is reported along with a discussion of the relevant literature.
A 50 year old male patient (D.K.), a farmer, was admitted to the K.E.M. Hospital, Bombay with complaints of distension of abdomen, loss of weight and appetite and oedema of the feet since 2 months. Bowels and micturition were normal.
On clinical examination, the general condition was satisfactory. Pedal oedema was present. There was no icterus or lymphadenopathy. The abdomen was grossly distended with no caput medusae or visible veins. Ascites with a large, non-tender hepatomegaly without splenomegaly was found.
The hemoglobin was 8.5 gm% with an ESR of 75 mm/first hour (Westergren); the blood urea nitrogen was 20 mg%, and blood sugar 100 mg%; liver function tests were within normal limits with a prothrombin time of 19/16 sec. The X-ray chest was normal and the 99mTc sulphur colloid liver scan showed cold areas in the inferior region of the liver. Ascitic fluid did not show any growth on culture and no malignant cells were detected on cytological examination.
On ultrasound imaging, multiple cystic areas were seen all over the abdomen, at least three in the liver, one in the spleen and one in the supra-umbilical region. Three of these showed multiple daughter cysts. The liver parenchyma was distorted. The gall bladder was normal but the common bile duct was dilated. Both kidneys were normal. Casoni's test was weakly positive. A presumptive diagnosis of multiple hydatid cysts was made. The patient was put on mebendazole 800 mg 8 hourly for 4 weeks and then explored. On laparotomy, the large cyst on the inferior aspect of the liver was opened. It showed many small cysts inside and contained necrotic and haemorrhagic material which was evacuated [Figs. 1] & [Figs. 1]. The walls were scraped and a large bore Malecot's catheter was inserted. Four similar cysts in the visceral peritoneum were also excised. There were many more cysts throughout the peritoneal cavity, which were extremely vascular, mucoid and adherent.
The patient made an uneventful postoperative recovery and was discharged with the Malecot's catheter in position. However, he succumbed 5 months later.
The cysts consisted of thickened peritoneal lining with the tumour on the inner side, consisting of two types of cells, spindle-shaped and epithelial like cells. The spindle cells were palisaded in one or two layers on papillary elements. The epithelial like cells were polyhedral, some were vacuolated and they were arranged in cords and in a tubulo-papillary pattern. The nuclei were hyperchromatic with occasional mitotic figures. Reticulin staining showed scanty reticulin fibres around groups of cells forming a papillary pattern [Fig. 3]. The mucoid substance was not stained by PAS with diastase but was strongly stained by the colloidal iron confirming the histological diagnosis of mesothelioma.
Mesothelioma is the only primary malignant tumour of the peritoneum. It is common in adults with a mean age, at presentation, of 50 years, but it is not unknown in children. Males predominate in all series. ,, Asbestos has been proved to be the main carcinogenic agent, as noted first by Wagner et al and later reported by many others,,, with a latent period of 1 to 50 years. Vulnerable occupations are shipyard workers, asbestos textile manufacturing, brake lining installation, insulation workers and sack repair workers. However, no history of asbestos exposure could be elicited in this case.
Symptomatology refers to the abdomen, with epigastric pain or burning, abdominal distress, abdominal distension and nausea or vomiting being common presenting symptoms. Severe weight loss is the rule and ascites, the most frequent clinical sign, is present in over 90% of the cases, while palpable masses are rarely found, Grossly, peritoneal mesothelioma may be indistinguishable from extensive carcinomatosis. Two basic forms are usually found. (1) A large tumour mass most often in the greater omentum with smaller nodules scattered over visceral and parietal peritoneum and (2) Diffuse nodules and plaques coating and obliterating the abdominal cavity with incorporation of all the viscera. When invasion occurs, it follows fascial planes. A large abdominal tumour may invade through the diaphragm and involve the pleura. Distant nodal metastases are uncommon; however, regional lymph node metastases are not infrequent. Observed sites of haematogenous spread include the liver, lungs and less commonly the kidneys and adrenals., In this case, the interesting feature was the gross appearance of multiple cysts simulating hydatid cysts. Mennemeyer and Smith described a case of peritoneal mesothelioma with a huge cyst resembling cystic lymphangioma. In this case the finding of a weakly positive Casoni's test led to the suspicion of hydatid cyst disease which, however, was conclusively proved wrong on histopathology.
Microscopically, the tumour ranges extensively from the pure epithelial type to the pure mesenchymal type with a spectrum of intermediate and combined forms. Histochemical studies showing acid mucoid substance such as hyaluronic acid helps in differentiating these tumours from other sarcomas and carcinomas. This material is found outside and around the cells. It does not stain with PAS, stains weakly with mucicarmine and strongly with colloidal iron, toludine blue or thionine giving metachromatic reactions.,,,, These reactions are considerably reduced by previous digestion with hyaluronidase., In specimens fixed in formalin as was ours, hyaluronic acid may be lost from the tissue and cytoplasmic vacuoles may be seen, which is noted in this case also.
Diagnosis is most often made after laparotomy and biopsy. Winslow and Taylor outlined the following criteria for establishment of the diagnosis of peritoneal mesothelioma: (1) compatible clinical history, (2) characteristic gross features, (3) characteristic microscopic features, and (4) progressive growth of the tumour leading to death.
Thompson and co-workers have suggested that high acid mucopolysaccharide level in sterile fluid with a non-diagnostic cytology strongly suggests mesothelioma.
It seems that awareness of the clinical condition of peritoneal mesothelioma by the surgeon and pathologist alike, may be a major factor in reaching a diagnosis. Treatment is generally unsatisfactory and most patients succumb within 12 months.,
We thank the Dean, Dr. C. K. Deshpande, and Dr. (Smt.) S. G. Kinare, Professor and Head, Department of Pathology, Seth G.S. Medical College and K.D.M. Hospital, Bombay for allowing us to publish this case.