Abstract: An elastically deformable marker (1) which can be completely implanted by means of a cannula for marking a tissue site, wherein the marker assumes a relaxed condition without an external force acting thereon and has at least one flexurally elastic wire, an elongate central marker portion and a proximal and a distal end portion, wherein a respective one of the two end portions is disposed at one of the two ends of the central marker portion, wherein in the elongate central marker portion at least two portions of the same flexurally elastic wire or a plurality of flexurally elastic wires are twisted together.

Abstract: A surgical instrument, in particular a marking instrument for marking body tissue, in particular tumor tissue, comprising a hollow needle for insertion into body tissue which encloses a lumen which is radially delimited by an inside wall of the hollow needle and which has an open mouth at the distal needle end, and at least one longitudinally displaceable element guided in the lumen, with distal end portions which have a pre-bend such that the distal end portions are elastically prestressed in the straightened condition and curve in the relaxed condition, wherein the distal end portions of the longitudinally displaceable element are to be pushed starting from a position of being retracted into the lumen, in which the distal end portions are straightened, out of the open distal mouth of the lumen and in so doing curve, wherein the longitudinally displaceable element is formed by a wire having a longitudinal slit, wherein the longitudinal slit extends from a base point at its proximal slit end to an open distal