Abstract: The invention relates to an optical biopsy instrument (100) comprising (a) a substantially cylindrical cannula (22) with a proximal end (24) and a distal end (26), said cannula (22) having at least one lateral opening (28), and (b) an endoscope (10) which is axially movable inside the cannula (22). The biopsy instrument (100) according to the invention permits, for the first time, a targeted removal of tissue samples (34) from narrow duct systems of the body, in particular from milk ducts of the breast, with optimal endoscopic visual monitoring.