[Pseudomyxoma peritonei: a case with multiple metastases. Ultrastructural study and chemical analysis of the mucoid...

A patient with spreading pseudomyxoma peritonei probably caused by a tumor of the appendix showing suggestive clinical features is presented. The long evolution was marked by the discovery of gelatinous substance in the stools and in the lumen of the gut, and the appearance of distant metastasis in the lungs, adrenal glands and lymph nodes. Histochemical studies showed that periodic Shiff acid and Alcian blue were fixed by the mucoid substance. The use of toluidin blue (pH 1) revealed metachromosia. Electron microscopy ascertained the presence of enterocytes and mucous cells and revealed a more obvious nuclear disorganisation than by histological microscopy. Biochemical study showed that the mucoid substance extracted from the pseudomyxoma was rich in carbohydrates and could be identified as a mucin on the basis of the composition of its monosaccarides and of the alkali-lability of its glycanprotein linkages. The mucin was weakly hydrolysed by trypsin in vitro but was deeply attacked by the same enzyme after desialylation. These results: a) confirm the possibility of observing spreading distant metastasis in the pseudomyxoma peritonei; b) underline the potential interest of electron microscopic study in case of wavering diagnosis; c) show that the mucoid substance belongs to the group of neutral sulfomucins; d) legitimate, in the future, a trial of palliative treatment by neuraminidase in such cases.