Elementary my dear Watson

We've been catching up on TV that we missed while we were out of town and tonight we had a mini Elementary marathon. During one episode, Joan (Watson) is talking to Sherlock about how she thought that maybe his father had cancer so she had started going through some pictures to see if she could find signs of cancer. In the story, she used to be a physician, so she's presented as someone with medical knowledge. So it made me wonder. What does that mean? Do I have the cancer "look"? I'm assuming that she meant sudden weight loss, maybe loss of hair, but what else?

I don't know, I feel like I look the same...