Let me say that I have node in my groing that is a little less that 2cm, so not huge, but not small either. I dont know how long it has been there, but I know for sure about six months. Has not grown. I also have a coworker with a rather large groing node and actually my boyfriend has one too. I dont think we all have lymphoma, just saying. I know its hard, but living with HA, I have learned that your body does not lie, you may ignore, but it does not lie. If you had something serious going on you would know.
So rest easy I know its hard, but my doctor told me the other day that the stress from my anxiety is going to kill me way before any disease. I listened. She said that constant stress is so hard on your body and it tears at your immune system. So I going to work very hard on bringing it down.
Anyhoo I hope this helps and you realize that groin lymph nodes are common, and although someone had stage 4 and it started witha groin node that the exception and not the rule. And of course we always feel that we will be the exception, and also I not sure but I the lymph node was likely pretty big when associated with cancer. I dont beleive you would have to dig around and find it. Just my thoughts. Good luck.