Urogenital mesenteric cyst with fallopian tubal features.

Urogenital cysts are retroperitoneal or mesenteric cysts that are derived from vestigial remnants of the embryonic urogenital apparatus. Although their precise embryonic origins are usually obscure, occasionally they display histologic features indicative of a mesonephric or metanephric origin. This report describes an unusual mesenteric müllerian cyst consisting of an endosalpingial lining and two-layered smooth muscle walls, probably representing a müllerian duct duplication cyst.