How Concerned Should We Be That Enlarged Nodes In The Neck Could Be Due To Cancer?

Question: My wife, 36 years old, went to her GP last week because of a persistent enlarged lymph node in her neck. Her doctor didn't seem too concerned about it, however she scheduled an ultrasound on her neck. It should be noted that my wife isn't experiencing any other issues such as fever, night sweats, weight loss, etc. Just the enlarged node. She had the ultrasound yesterday and they told her that the node was 4cm and that she had three others on the other side of her neck that were just north of 1cm. They said the radiologist will look at it to determine if a biopsy is necessary. My question is this...how concerned should we be that it's something as serious as cancer? The 4cm node has been swollen for close to 6 months but, again, no other symptoms. Her mother was recently diagnosed with Merkel Cell so there is apparently some history there. We are obviously very frightened and are seeing what the odds/chances are that it could be cancer. We know that without a biopsy it's impossible to know for sure, but until then, we are just looking for some information. Thank you.

Okay, thank you. This is very scary for us so thank you for your help.