Fig. 6

a Splitting of muscularis mucosae (mm) creates a space between duplicated muscle fibers and superficial/inner and a deep/outer layer of muscularis mucosa in Barrett’s esophagus; Thick arrow marks submucosal vessels. b Potential over interpretation of level of invasion of a T1a adenocarcinoma invading into the space in between duplicated muscualris mucosae as pT1b (submucosal invasion) or pT2 (muscularis propria invasion).