I have had a reactive lymph node in my right armpit for 2 weeks now. I saw a GP last week who confirmed it is a reactive lymph node, to monitor it for 2 weeks and check breasts for any lumps (which I cannot feel), and then to return if there is no decrease (or an increase) in size of the node. So far, there is no change to the size of the lump in my armpit. 

How many people have been diagnosed with cancer based only on a reactive lymph node being the only symptom?

I don't have any other symptoms, but I have convinced myself through Googling that I have cancer. I am so worried, I cannot stop thinking about it! Whilst the chances are low, they are obviously not impossible and I do not know how to keep calm about it. I have a 5 and 3 yr old, I cannot cope with the thought that I wouldnt be around to see them grow up.