<s>[INST] I have just discovered a large lump in my 6 yr old sons neck, to the left towards the back of his jaw.  He says he feels fine, he doesnt have a temperature and is eating as usual.  I would say however that he has been looking pale for a while and has dark circles under his eyes.  He has a bakers cyst on the back of his knee, which was diagnosed and scanned about a month ago.I am very concerned and have just called our GP who can see him this afternoon.  Lymphoma and Leukemia run in my family.Yours,Jane Maben [/INST] Hi. Thanks for your query and an elucidated history. History noted. I would suggest for a simple test of FNAC= fine needle aspiration cytology. This will help immensely to confirm or rule out a sinister problem of lymphoma. Blood picture would help for leukemia. Towards the back of the jaw can be more of a parotid swelling than the lymph node. The treatment will be totally dependent on what will be reports. </s>