A biopsy instrument comprising a base member which extends from a proximal end to a distal end along a central geometrical axis, wherein at least a distal end portion of the base member is shaped as an elongated hollow tube, the distal end being intended to be at least partly inserted into a tissue from which a biopsy is to be obtained, wherein the base member is capable of transferring a force along the central geometrical axis such that a movement (LF, LB) of the proximal end along the central geometrical axis is transferred to a movement (LF, LB) of the distal end along the central geometrical axis, and of transferring a torque about the central geometrical axis such that a rotation (ω) and a torque applied by a motor at the proximal end about the central geometrical axis is transferred from the proximal end to the distal end thereby rotating the distal end about the central geometrical axis, wherein the hollow tube is provided with a distally facing circular cutting edge defining a mouth of the distal end of the hollow tube, characterised in that the distally facing circular cutting edge has, as seen along a circumference of the mouth, a straight-line configuration, that the mouth defines a plane having a normal parallel to the central geometrical axis as the central geometrical axis passes through said plane of the mouth, that the hollow tube has, at a distal portion of the hollow tube, a hollow elongated tubular sample acquiring portion having a smooth interior surface, wherein the smooth interior surface is smooth to such an extent that when a reference biopsy is to be acquired, the cutting edge and the distal end of the hollow tube being configured to be advanced along the central geometrical axis into a tissue while being rotated (ω, T) by being motor driven at its proximal end and thereby cutting a core of the tissue which, due to the advancement of the hollow tube, enters relative to the hollow tube through the mouth into the sample acquiring portion of the hollow tube with a circumferential outer surface of the core at least partly abutting the smooth interior surface of the sample acquiring portion, where-after the hollow tube is retracted from the tissue while being rotated (ω, T) by being motor driven at its proximal end whereby the core of the tissue is detached from the tissue by a pulling force due to the retraction of the hollow tube and due to an adhesive force formed at an interface between the smooth interior surface and the circumferential outer surface of the core which force keeps the core inside the sample acquiring portion having the smooth interior surface, and the biopsy instrument further characterized by being configured such that during the advancement and retraction of the hollow tube, the hollow tube is rotated in the same rotational direction. a base member which extends from a proximal end to a distal end along a central geometrical axis, wherein at least a distal end portion of the base member is shaped as an elongated hollow tube, the distal end being intended to be at least partly inserted into a tissue from which a biopsy is to be obtained, wherein the base member is capable of transferring a force along the central geometrical axis such that a movement (LF, LB) of the proximal end along the central geometrical axis is transferred to a movement (LF, LB) of the distal end along the central geometrical axis, and of transferring a torque about the central geometrical axis such that a rotation (ω) and a torque applied by a motor at the proximal end about the central geometrical axis is transferred from the proximal end to the distal end thereby rotating the distal end about the central geometrical axis, wherein the hollow tube is provided with a distally facing circular cutting edge defining a mouth of the distal end of the hollow tube, characterised in that the distally facing circular cutting edge has, as seen along a circumference of the mouth, a straight-line configuration, that the mouth defines a plane having a normal parallel to the central geometrical axis as the central geometrical axis passes through said plane of the mouth, that the hollow tube has, at a distal portion of the hollow tube, a hollow elongated tubular sample acquiring portion having a smooth interior surface, wherein the smooth interior surface is smooth to such an extent that when a reference biopsy is to be acquired, the cutting edge and the distal end of the hollow tube being configured to be advanced along the central geometrical axis into a tissue while being rotated (ω, T) by being motor driven at its proximal end and thereby cutting a core of the tissue which, due to the advancement of the hollow tube, enters relative to the hollow tube through the mouth into the sample acquiring portion of the hollow tube with a circumferential outer surface of the core at least partly abutting the smooth interior surface of the sample acquiring portion, where-after the hollow tube is retracted from the tissue while being rotated (ω, T) by being motor driven at its proximal end whereby the core of the tissue is detached from the tissue by a pulling force due to the retraction of the hollow tube and due to an adhesive force formed at an interface between the smooth interior surface and the circumferential outer surface of the core which force keeps the core inside the sample acquiring portion having the smooth interior surface, and the biopsy instrument further characterized by being configured such that during the advancement and retraction of the hollow tube, the hollow tube is rotated in the same rotational direction.