The present invention relates to a surgical instrument (1) for sampling molecules from an organ to which access is possible directly or via a surgical approach, including: a device (5) for capturing said molecules, a stylus (4) supporting said capture device (5) and which is capable of penetrating the organ, and a guide (3) for inserting the stylus (4) into the body up to the organ, characterized in that the distal end of the guide (3) is provided with a damping block (6) intended to bear against the organ.
