Recurrence in Abdominal Wall

Hello all- my husband was diagnosed with colon cancer in March 2016. He was admitted at our local emergency and it was discovered he had the mass the size of an orange in his colon. They attempted to do a colonoscopy/sigmoidoscopy to get a better look, but he was almost totally blocked. the y did surgical resection and ostomy. He did 12 rounds of Folfox for a Stage 2 with no nodes and completed in December of 2016. He was going every 3 months for scans when this past October they wanted to get a closer look at what they thought was a benign growth in the area which was the prior site of his ostomy (Since reversed). More cat and pet scans and it was decided to do a biopsy of a mass about 3.5 (size of a grape tomato) in his abdominal wall. The biopsy revealed it was an ademocarcinoma- the same as what was in his colon. He went back to the original surgeon and had a surgery to remove it on January 4th. The surgeon took out the mass and a lot of scar tissue from the previous surgery on the ostomy. A small amount of mesh was implanted in the wall similar to hernia surgery because he took margins and wanted to be sure that the wall was supported after taking out the tissue. We just found out that the cancer had approached one of the margins and couldn’t be classified as clean. The onc spoke to an rad/onc and it isn’t a viable location for radiation treatment. He is speaking with the surgeon tomorrow as he would like the doc to go back in and take more tissue at the offending margin. The onc is saying that my husband will definitely have to do chemo. We have an existing appointment with the surgeon tomorrow to remove the staples from the previous surgery. My question is, say the surgeon does go back in...if that is even a possibility...how does he know where to take from? Meaning, which side of the margin was the offender? I feel like it is Ground Hogs Day...why is this happening again??  Everything else is clear...liver...lungs..etc. I am a mess. Completely fell apart after phone call from oncologist. How does this migrate to the abdominal wall?? I am lost, confused and totally upset. I am finding it hard to live in the moment right now and can’t help but go to dark places. I apologize for the length of this post. To add insult to injury. My little sister was diagnosed with breast cancer only 3 days prior to this recurrence of my husband’s cancer. As I said, I am lost.