I am at 33 year old female who has a lump on my left side of my neck above my collarbone.?

It is hard, non-moveable and has grown since I first noticed it five weeks ago. It feels as though it is two different sized lumps fused together. I had a cat-scan with IV contrast on Tuesday and extensive blood work. The doctor's office called today and indicated that I have a 4cm reactive node and want me to get a biopsy done. The nurse did not provide further information, even with my prompting. Can a reactive node be malignant? What are some causes of a reactive node? I am reading that it can be viral or bacterial infection, but my lump consistency has me concerned that it is cancerous. I see that viral and bacterial are usually moveable, go away and are not hard. Is this true? Also, would the lump continue to grow if not malignant? The anxiety is killing me. I also found out a cousin had Hodgkin's disease when he was 21. Is it hereditary? I truly appreciate any insight. Thanks!