A tissue ablation system comprises a first electrode assembly adapted for insertion into a target tissue mass within a body, the first electrode assembly including a first electrode coupled to a source of RF energy in combination with an ultrasound imaging probe movably coupled to the first electrode assembly for insertion with the first electrode assembly to a desired location relative to the target tissue mass, the probe being movable relative to the first electrode assembly between an insertion configuration in which a distal end of the probe covers a distal end of the first electrode assembly and a deployed configuration in which the distal end of the first electrode assembly is uncovered. A method of ablating target tissue within a body comprises placing a distal dome of an ultrasound imaging probe in overlying alignment with a first cannula of an RF ablation device and inserting the probe and the RF ablation device through a lumen of an insertion device to a desired location adjacent to a target tissue mass in combination with moving the distal dome away from a distal end of the first cannula to expose a distal end thereof, inserting the distal end of the first cannula into the target tissue mass to position a first electrode of the RF ablation device at a first desired location within the target tissue mass, obtaining an image of the target tissue mass and the first electrode via the probe and applying RF energy to the target tissue mass via the first electrode.