[Severity of desmoid tumors with retroperitoneal development in Gardner's syndrome. Apropos of 2 cases].

We report two cases of retroperitoneal desmoid tumours in patients with Gardner's syndrome. These tumours are rare and of poor prognosis. In our two cases, the predominant clinical manifestations were caused by compression of the ureters, bladder and nerve roots. In the first patient, the tumours developed after colectomy, while in the second patient the discovery of the desmoid tumour preceded that of a cancer of the colon. Finally, in the first patient, an attempted treatment with a non-steroidal anti-inflammatory agent (sulindac) had to be discontinued after 4 months on account of side-effects.