PMC9530747_01
Flexible colonoscopy revealed the two tumors at the rectal anastomosis site of PPH. One tumor was indicated by a red circle, and the other tumor was indicated by a blue circle. (A-C): bright light image; (D-F): narrow band image; follow-up colonoscopy performed at 1 month (G), 3 months (H), and 8 months (I) after TEM.
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Flexible colonoscopy (9 March 2019) revealed two tumors at the rectal anastomosis of PPH ( Figure 1 ); the sigmoid anastomosis and remaining colorectal mucosa appeared to have normal results. TEM ( Figures 1G-I  ).
The timeline of important events, treatment, and follow up.
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The patient was last followed up on 26 April 2022 by telephone interview, and she had remained disease-free (without local recurrence or distant metastasis) for 3 years after TEM. The timeline of important events, treatment, and follow up is shown in  Figure 2 .
LICHeE analysis was used to assess the diversity using single-nucleotide variants in the three tumor tissues. (A) Each circle indicates a clone. The arrow indicates evolutionary direction. The number in the circle indicates the number of variants. GL indicates germline mutations, representing healthy tissues. Colors in squares indicate compositions of clones. Samples sharing common clones in the early stage indicate the presence of metastasis. (B) Color bar on the left: each color bar represents a clone, and the length of the color bar represents the number of variants. Color line on the right: the root (red) represents healthy tissues, and the end represents tumor tissues. Tissue with common variants indicates the presence of metastasis.
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Therefore, LICHeE analysis was used to assess the diversity using single-nucleotide variants obtained from the three tumor tissues ( Figure 3A ) and showed that the R1 and R2 tumors were probably implantation metastases arising from the S tumor ( Figure 3B ).