Fig. 3

Histopathological findings (area enclosed by the dashed red line in Fig. 2b). a, b Hematoxylin and eosin (H&E) staining findings. The wall thickening is attributable to the thickness of the muscular layer (area enclosed by the dashed black line). The esophageal tumor is a squamous cell carcinoma. c, d α-smooth muscle actin [α-SMA] staining findings. The increased thickness of the muscular layer is caused by the increased number of smooth muscle. e, f Cytokeratin 34βE12 staining findings. Squamous cell carcinoma invading the muscularis propria (blue arrow)