A twin-cannula fat tissue aspiration instrument system equipped with a hand-supportable fat aspiration instrument having a twin irrigating-type or tumescent-type electro-cauterizing cannula assembly with an inner cannula coupled to a cannula drive mechanism and having an inner aspiration aperture that is reciprocated within an outer cannula having an outer aspiration aperture and being connected to the front portion of the hand-supportable housing, so that said inner cannula reciprocates within said outer cannula when the cannula drive mechanism drives the inner cannula. An irrigation channel is formed along the outer cannula, and in fluid communication with an irrigation aperture formed at the distal portion of the outer cannula and proximate to the outer aspiration aperture. Also, electrodes are disposed about the outer aspiration aperture for delivering RF signals aspirated fat tissue being aspirated through the outer and inner aspiration apertures so as to electro-cauterize said aspirated fat tissue during irrigation operations.