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Page 4 of 8 Hayashi et al. Mini-invasive Surg 2022;6:7 https://dx.doi.org/10.20517/2574-1225.2021.125

Figure 2. Changing the vertical orientation to horizontal after aspirating the gas. (A) A tumor is on the vertical wall. (B) The wall
becomes horizontal after collapsing the intestine by aspirating gas.

Figure 3. The submucosa thickens after aspirating the gas. (A) The submucosa is stretched and thinned in the insufflated intestine. (B)
The submucosa thickens in the collapsed intestine.

damage the tumor. However, a longer tumor-side edge allows for greater traction [Figure 4]. Then, the
endoscope goes downward gradually to reach the bottom of the submucosal layer. Even if the longer edge is
accidentally torn by traction, it will have a margin at a distance. Coagulation when dissecting the submucosa
below the tumor burns and scars the submucosa, which tends to make the tumor-side edge rolled. Rolling
makes it difficult for the endoscope tip to flip up the edge and apply upward traction.

Successive short dissections make a safe and precise dissection line
When starting to dissect the submucosa, hooking the submucosal tissue a slightly in the direction of the
planned cut maintains a safe distance from both the muscularis and beneath the tumor. Then, press the
pedal of the diathermy unit for a slightly less than one second, in order to make a short dissection. It is
necessary to press it for the appropriate coagulation time, not extremely short, to avoid immediate bleeding
from small blood vessels. Repeat multiple short dissections result in a safe and precise dissection line
[Figure 5].

An example of performing PCM
A locally recurrent tumor in the rectosigmoid portion was found 6 years after multiple endoscopic
piecemeal mucosal resections for cancer in an adenoma at another hospital [Figure 6]. Although the tumor
had severe central submucosal fibrosis, PCM could deal with the fibrosis and achieved a complete resection.
The resected specimen was 105 mm in diameter. Pathology revealed a high-grade adenoma with a negative
margin.

DISCUSSION
It has been shown through retrospective studies and a prospective randomized control study that PCM
facilitates colorectal ESD [3,5-7,10] . When comparing PCM to the conventional method, PCM has significant