Prospective multicenter study on the usefulness of EUS-guided FNA biopsy for the diagnosis of autoimmune pancreatitisProspective multicenter study on the usefulness of EUS-guided FNA biopsy for the diagnosis of autoimmune pancreatitis 自己免疫性膵炎の診断における超音波内視鏡下穿刺吸引生検の有用性に関する多施設共同前向き研究