Abstract: A tissue treatment system has a handheld treatment instrument that generates a gas plasma jet for delivering thermal energy to a tissue surface to be treated. Incorporated in the handpiece is an optical target marking projector for projecting a visible target marker onto the tissue surface when spaced from a distal end of the handpiece. The marker indicates a treatment area and is generated by illuminating an apertured mask and transmitting light from the mask via an optical fibre guide to an exit aperture adjacent a gas plasma nozzle of the instrument. A method regenerates the reticular architecture of tissue whilst illuminating the treatment area using the target marker.