Pathologic Quiz Case: A Large Mesenteric Mass in a 40-Year-Old Man

A man sought medical attention for vague flank pain. His past medical history was significant for mucinous cystadenoma of the appendix (status 11⁄2 years postappendectomy with intraoperative right ureter injury). A computed tomographic scan at this presentation revealed fibrosis surrounding the right ureter, which had produced right hydronephrosis (Figure 1). These changes were believed to be the result of prior surgical injury to the ureter during appendectomy and were managed by ureteral stenting. Strikingly, a 7.5-cm lesion was incidentally identified on computed tomographic scan in the region between the pancreatic tail, left kidney, and spleen, with a small entrapped accessory spleen (Figure 1). The