If your surgeon is good he should know what to cut. Usually they are aided by a ct scan - I would not want to be a dr relying on potential clear margins based off a previous surgery - it's best to know what to cut. Some CCCs have a newer technology where they can see the cancer in real time. (While they're cutting) my dr. Pioneered this technique. Some still do it the old fashioned way based off a scan - and then cutting a larger area than shown on the scan. This definitely has it's draw backs. Ask your surgeon what he bases his surgery location on.

Did your mom have a neck dissection with her previous cancer? If she didn't I home they've schedule her for one as well.

Hugs