A biopsy forceps tool (preferably for endoscopic use) in which microwave energy is used to coagulate bleeding after a biological tissue sample is collected between a pair of jaws. The pair of jaws define an enclosure that is isolated from the microwave energy itself and insulated from any thermal changes that occur due to application of the microwave energy. The tool comprises a pair of jaws connected to a coaxial cable, each of the pair of jaws comprising an electrically conductive shell, the jaw assembly being movable between a closed position in which the electrically conductive shells enclose an internal volume for holding a tissue sample and an open position in which the internal volume is exposed in order to receive the tissue sample. The electrically conductive shells form a Faraday cage around the internal volume when in the closed position.