Woman asks if I'm my sons grandma

I was at the grocery store last week with my 4yo son. I'm 40 and I just survived stage 4 lymphoma, a massive abdominal surgery, and a bone marrow transplant. An older woman in the store stopped my son and asked if he was having a nice day out with grandma. I was shocked for a moment and then said "nope this is just what surviving stage 4 cancer looks like." Her speechlessness was all the reward I needed.