502 Choi et al FIG. 1. Preoperative computed tomo- graphy imaging. The contrast-enhanced coronal reformatted image depicts moderate enhancing fibrous tissue (arrow 2) with right ureteral stenosis (arrow 1). FIG. 2. Histopathological findings. (A) Grossly, the excised mass was ill-defined and adhered to the small and large in- testine (ileocecal valve). (B) Excised ureteral mass. (C) Mesenteric fibro- matosis showing cytologically bland spindle cells in a collagenous stroma (H&E, x200). (D) The cells showed posi- tive nuclear staining for beta-catenin (Immunohistochemical staining, x200). the lesion was poorly circumscribed, with infiltration of the surrounding fat tissue, and was composed of cytologically bland, elongated, slender, spindle-shaped cells with collag- enous stroma containing vessels of varying size. The cells were arranged in sweeping bundles and were admixed with a storiform growth pattern (Fig. 2). The cells lacked cyto- logic atypia or nuclear hyperchromasia and had vesicular nuclei with minute nucleoli. The mitotic figure was rare. In immunohistochemical staining, the spindle- shaped cells revealed nuclear β-catenin staining and focally pos- itive staining for smooth muscle actin (SMA). However, the spindle-shaped cells were negative for C-kit (CD117), CD34, desmin, and S-100. Given the histopathological findings, a diagnosis of mesenteric fibromatosis was con- firmed (Fig. 2). 　The patient was discharged 5 days after surgery without Korean J Urol 2010;51:501-504