RT Journal A1 HELLSTROM H, FISHER ER T1 BEnign retroperitoneal mesenchymoma (hamartoma) JF A.M.A. Archives of Surgery JO A.M.A. Archives of Surgery YR 1959 FD June 1 VO 78 IS 6 SP 975 OP 978 DO 10.1001/archsurg.1959.04320060163027 UL http://dx.doi.org/10.1001/archsurg.1959.04320060163027 AB Retroperitoneal cysts are rare, approximately 70 such lesions having been recorded.1 Examples have been classified as (1) lymphatic, (2) enteric, (3) urogenital, (4) teratoid, (5) parasitic and inflammatory, and (6) traumatic.2 The vast majority of these cysts have been considered to be lymphatic in origin,1,3-7 and have variously been termed chylous cysts,2,3,6,8 lymphatic cysts,9,10 or cystic lymphangiomas.1,5These tumors are usually asymptomatic, and most frequently present as an abdominal mass.1,2 Occasionally, the symptoms of intermittent partial intestinal obstruction, peripheral edema, or poorly localized abdominal pain may occur as a result of pressure on bowel, blood vessels, or nerves.2 Rarely, torsion of the pedicle of the cyst may result in actue abdominal pain, simulating other abdominal catastrophes.1,2The purpose of this report is to describe a retroperitoneal cyst formed predominantly of lymphangiomatous elements, but which contained other structures, such as arteries, veins,