A surgical instrument for ablating tissue includes a handle portion and a shaft assembly extending distally from the handle portion. The shaft assembly includes an outer shaft, a coaxial cable extending through the outer shaft, and an electrode coupled to a distal portion of the outer shaft. The coaxial cable has a distal portion that forms a microwave antenna configured to transmit microwave energy radially outward and through the outer shaft. The electrode is configured to transmit radiofrequency energy. An actuation of the handle portion activates the transmission of the microwave energy from the microwave antenna and/or the transmission of the radiofrequency energy from the at least one electrode.
