Fig. 2

Estimation of the intramural spread distance between visible margin and microscopic margin. A Schematic explanation for positive spread distance, Step 1: the black line was visible tumor margin under naked eyes. Step 2: the red line was a microscopic tumor margin under the microscope. Step 3: red double arrow length was tumor cell intramural spread distance, which is the distance between the visible tumor margin and the microscopic margin. Black little dots between the visible margin and the microscopic margin were scattered tumor cells. The blue line was a safe distal resection margin. B Schematic representation of the negative spread distance. The red, black, and blue lines and small black dots indicate the same results as indicated in A. There was swollen abnormal tissue, so the visible tumor margin was labeled at the distal edge of the abnormal tissue. C The pathological explanation for positive spread distance, corresponding to A. White arrow was the carbon nanoparticles, which indicated visible tumor margins under naked eyes. Black arrow was the furthest scattered tumor cells. D The pathological explanation for negative spread distance is shown in B