An endoscopic tool (100, 200, 300, 400, 500, 600, 700) for facilitating injection of a fluid into a submucosal layer of tissue, the endoscopic tool comprising: a first cannula (124, 224, 324, 524, 724) adapted to be slidably disposed within a lumen of an endoscope, the first cannula having a suction surface and a suction lumen (148, 248, 348, 448, 548, 648), the suction surface disposed at a distal end of the first cannula to contact a mucosal layer of tissue, the suction lumen formed within the first cannula between the suction surface and a proximal end of the first cannula; a second cannula adapted to be coupled to a source of a fluid (788, 912) to be delivered to the submucosal layer of tissue below the mucosal layer of tissue, the second cannula carrying a needle at a distal end of the second cannula; and a suction source coupled to the first cannula (124, 224, 324, 524, 724) to create a negative pressure within the suction lumen to draw the mucosal layer of tissue into contact with the suction surface and hold the mucosal layer of tissue against the suction surface, wherein responsive to the mucosal layer of tissue contacting the suction surface, the second cannula is movable toward the submucosal layer of tissue, causing the needle to pierce the mucosal layer of tissue and deliver the fluid into the submucosal layer of tissue; characterized in that the endoscopic tool further comprises a needle stabilization structure (168, 268, 368, 468, 568) coupled to the first cannula (124, 224, 324, 524, 724) or the second cannula, the needle stabilization structure defining a fluid lumen (132, 332, 432) separate from the suction lumen, the second cannula slidably disposed within the fluid lumen. a first cannula (124, 224, 324, 524, 724) adapted to be slidably disposed within a lumen of an endoscope, the first cannula having a suction surface and a suction lumen (148, 248, 348, 448, 548, 648), the suction surface disposed at a distal end of the first cannula to contact a mucosal layer of tissue, the suction lumen formed within the first cannula between the suction surface and a proximal end of the first cannula; a second cannula adapted to be coupled to a source of a fluid (788, 912) to be delivered to the submucosal layer of tissue below the mucosal layer of tissue, the second cannula carrying a needle at a distal end of the second cannula; and a suction source coupled to the first cannula (124, 224, 324, 524, 724) to create a negative pressure within the suction lumen to draw the mucosal layer of tissue into contact with the suction surface and hold the mucosal layer of tissue against the suction surface, wherein responsive to the mucosal layer of tissue contacting the suction surface, the second cannula is movable toward the submucosal layer of tissue, causing the needle to pierce the mucosal layer of tissue and deliver the fluid into the submucosal layer of tissue; characterized in that the endoscopic tool further comprises a needle stabilization structure (168, 268, 368, 468, 568) coupled to the first cannula (124, 224, 324, 524, 724) or the second cannula, the needle stabilization structure defining a fluid lumen (132, 332, 432) separate from the suction lumen, the second cannula slidably disposed within the fluid lumen.