What to say when someone tells you they are dying?

I have had people say shocking things to me before regarding health, but I have never experienced the type of situation I did today. In my day job, I am a project manager for a major wireless telecommunications call, and I joined a weekly conference call held on Thursday's about a pretty mundane topic. The call leader kicked off the meeting with sadly informing us that her cancer has come back and it is now in her lungs and liver. She stated that even though she was taking rounds of chemo, the prognosis was not very good and her doctor told her to get her affairs in order. Then explained that one of her co-workers would be taking over the series going forward, and then proceeded through with her normal action item updates on the call.

What can I say to a virtual stranger that I have never met in person in a situation where it is a very personal tragic situation being shared in a public work forum? I was speechless and shocked. I mean, what could I even say on the call that would have come across as heartfelt and compassionate as I wanted it to be? I am still at a loss for words. I am in at awe of people being able to share such personal situations with others. I don't know if I could do that with co-workers, but I think it depends on the person and the immediate situation. My co-worker needed to express this to us, and I commend her for her courage to share it. I try to look at situations on what is the lesson I should learn from them, and I don't know if in this situation that has more of a lesson for me than "just being there" on that call at that time. I just don't know...