Differentiation grade as a risk factor for lymph node metastasis in T1 colorectal cancer oleh Osamu Shiina, Shin‐ei Kudo, Katsuro Ichimasa, Yuki Takashina, Yuta Kouyama, Kenichi Mochizuki, Yuriko Morita, Takanori Kuroki, Shun Kato, Hiroki Nakamura, Shingo Matsudaira, Masashi Misawa, Noriyuki Ogata, Takemasa Hayashi, Kunihiko Wakamura, Naruhiko Sawada, Toshiyuki Baba, Tetsuo Nemoto, Fumio Ishida, Hideyuki Miyachi