A needle insertable into biological tissue, the needle having: an elongate body terminating with an insertion tip; a longitudinal channel formed within the body for transporting material to or from the tissue; and characterised by: a coaxial antenna comprising an inner conductor along the inside wall of the channel and an outer conductor coaxial with the inner conductor and separated from it by a dielectric material, wherein the longitudinal channel extends through the insertion tip and terminates at an opening in the insertion tip, wherein the coaxial antenna is arranged to produce a microwave radiation field to couple microwave energy received from a microwave power source via a microwave connector to biological tissue at the insertion tip, wherein the insertion tip comprises a rigid ceramic element which is attached to the dielectric material of the coaxial antenna and extends out of the outer conductor at a distal end of the elongate body, wherein the needle includes a metal stub or swage mounted on the dielectric material of the coaxial antenna at a location proximal to the rigid ceramic element, and wherein the rigid ceramic element and the metal stub or swage in combination provide a matching transformer for matching the impedance of the coaxial antenna to a predetermined representative tissue impedance at a predetermined frequency of microwave energy. an elongate body terminating with an insertion tip; a longitudinal channel formed within the body for transporting material to or from the tissue; and characterised by: a coaxial antenna comprising an inner conductor along the inside wall of the channel and an outer conductor coaxial with the inner conductor and separated from it by a dielectric material, wherein the longitudinal channel extends through the insertion tip and terminates at an opening in the insertion tip, wherein the coaxial antenna is arranged to produce a microwave radiation field to couple microwave energy received from a microwave power source via a microwave connector to biological tissue at the insertion tip, wherein the insertion tip comprises a rigid ceramic element which is attached to the dielectric material of the coaxial antenna and extends out of the outer conductor at a distal end of the elongate body, wherein the needle includes a metal stub or swage mounted on the dielectric material of the coaxial antenna at a location proximal to the rigid ceramic element, and wherein the rigid ceramic element and the metal stub or swage in combination provide a matching transformer for matching the impedance of the coaxial antenna to a predetermined representative tissue impedance at a predetermined frequency of microwave energy. a coaxial antenna comprising an inner conductor along the inside wall of the channel and an outer conductor coaxial with the inner conductor and separated from it by a dielectric material, wherein the longitudinal channel extends through the insertion tip and terminates at an opening in the insertion tip, wherein the coaxial antenna is arranged to produce a microwave radiation field to couple microwave energy received from a microwave power source via a microwave connector to biological tissue at the insertion tip, wherein the insertion tip comprises a rigid ceramic element which is attached to the dielectric material of the coaxial antenna and extends out of the outer conductor at a distal end of the elongate body, wherein the needle includes a metal stub or swage mounted on the dielectric material of the coaxial antenna at a location proximal to the rigid ceramic element, and wherein the rigid ceramic element and the metal stub or swage in combination provide a matching transformer for matching the impedance of the coaxial antenna to a predetermined representative tissue impedance at a predetermined frequency of microwave energy.