A case of spontaneous isolated mesenteric fibromatosis presenting as m
egaduodenum is reported. The lesion was small, only 2 cm in its greate
st diameter. However, because of its location near the ligament of Tre
itz and because of its characteristic infiltrative growth pattern, the
tumour involved the distal duodenum and resulted in acute angulation
and obstruction early in its course. We successfully resected the mass
and the patient is in fair physical condition 6 months after operatio
n.