There are disclosed embodiments of a system for thermochemical tissue ablation. An ablation needle in the form of a cannula with a tip and a plurality of tubes or lumens therethrough is provided, with the tip forming a hollow mixing chamber without external openings. Liquid reagents are passed through the lumens or tubes to the mixing chamber, where an exothermic reaction results, heating the tip. The heated tip is used for tissue ablation. The reaction product can be at least partially evacuated from the mixing chamber through a tube or lumen that empties into a container.