Abstract: A tissue ablation device includes an ablation stem insertable into the working channel of a medical device such as endoscope for radiofrequency ablation of target tissue. The stem includes a sheath, cannula, and ablation wire concentrically disposed within one another. Each of the sheath, cannula and ablation wire are independently controllable by a dedicated positioner located in the handset. An end effector of tines is removably attached to the distal end of the ablation wire and expand radially outwardly when deployed to form a three-dimensional ablation zone. A motor provides repetitive reciprocating vibrations to generate axial displacement of the ablation wire and tines for increased accuracy in insertion into tissue. RF ablation is also provided through the ablation wire and tines. The end effector tines are removable to remain in the target tissue as a fiducial marker for later procedures.