An endoscopic instrument according to the invention includes an elongate tube, which has an axially continuous and substantially cylindrical main lumen for receiving a shaft of an endoscope lens system, and a tool, which is arranged at a distal end of the tube and can be controlled via an elongate transmission element from a proximal end of the tube, wherein the tube has an axially continuous secondary lumen which adjoins the main lumen in a transverse direction, is connected to the main lumen via a narrowed transition area and receives the transmission element. The invention also relates to an endoscopic instrument system.
