What Causes Facial Lymph Nodes To Swell?

Hi there! I have a swollen lymph node on right side of my face in front of my ear.. It's been like this for a few weeks now.. It isn't sore or causing me any bother at the minute.. I just feel like I look weird when I look into the mirror... I have an Immune disease already called myositis or something like that at present I take 1000mg of cellcept twice daily.. Do you think this could be a tumour?? Thanks