swelling above my collar bone with small hard centre

Hi all,
I have a swelling the size of a tennis ball just above my collar bone on the left side, it is soft and has not got any bigger over the years, but it has a hard bean shaped lump in the middle of it about 1.5cm ? a lymph node. I just thought it was a lipoma as I have another small one on my temple. It has been there about 3 years but the hard lump inside it has grown in size over the last 12 months. It is not sore and does not bother me in any way. I am a healthy 53 year old female and have no other symptoms. I have read lots on the internet about swollen lymph nodes in the supraclavical area and they are 90% of the time cancerous, but I am not convinced mine is a lymph node. I saw a GP today who has ordered an ultrasound next week, he also said it is unusal to have the surrounding swelling if it was a lymph node, but offered no other explanation. Any ideas?