I am putting this post out here to see if anyone has experienced the same thing as we are going through right now. My daughter has had a large, solid mass behind her knee for what we know atleast 6 weeks. This mass is unmovable and is growing . After several visits with the doctor and not really being listened too a doctor eventually had a proper feel and suspects possible cancer. We have been put on an urgent referral and a x-ray is being done this week and we have another appointment the following week. The anxiety/ waiting is quite frankly unbearable and we are all struggling massively. My poor daughter has only just turned 4. Has anyone experienced this and what was the outcome. The doctor has said this is definitely not a cyst and is connected a lot deeper so this rules out bakers cyst, Thankyou