DCIS - Breast marker missed in initial surgery

Insist on a refund. If I took my cat to the vet to have a hairball surgically removed, and found that they had cleaned her teeth instead, there is no way in hell I'd pay for it. You paid him good money to remove your DCIS. He didn't. He removed perfectly healthy breast tissue instead and left the diseased area behind. He didn't complete his portion of your mutual contract. Tell him a coffin costs more.