A large area thermal ablation apparatus for use with an endoscope includes a housing and at least one electrode. The housing is removably attachable to a distal terminating end of the endoscope. The housing includes an outer surface and a cross-sectional area that is at least as large as a cross-sectional area of the distal terminating end of the endoscope. The electrode is supported by the outer surface of the housing. The electrode is capable of delivering energy to a tissue region inside a body to ablate the tissue region.