UNUSUAL conditions are worthy of reporting if they are likely to be forgotten in differential diagnosis, with resultant delay or confusion in rendering proper treatment. Such is the case as regards mesenteric cysts which are uncommon enough to be neglected in both teaching and practice. DEFINITION Thompson and Chambers10provide a reasonable definition of chylangioma as a tumor of lymph vessels which consists of an anastomosing network of lymph spaces supported by thin walls or thick septa. It is lined by epithelium and contains chyle or more inspissated fatty material which is often bloodstained. It may be unilocular or multilocular and, as pointed out by Block,3must be differentiated from congenital duplication of the bowel, which it may closely resemble. It may vary in size from a diameter of 3 or 4 cm. to a tumor occupying a large part of the abdominal cavity. INCIDENCE Beahrs1states