A microwave antenna assembly comprising an elongate shaft having proximal and distal ends and a lumen defined therebetween, a conductive member at least partially disposed within the inner lumen of elongate shaft, conductive member being selectively deployable relative to a distal end of elongate shaft from a first condition wherein a distal end of conductive member at least partially abuts the distal end of elongate shaft to a second condition wherein the distal end of conductive member is spaced relative to the distal end of elongate shaft and a first dielectric material disposed between elongate shaft and conductive member, wherein a portion of conductive member is distal to the distal end of elongate shaft and adapted to penetrate tissue.