<s>[INST] Hi. I am a 24 year old female. I have noticed within the past year I have these knots (or lumps) on the back of my head. Sometimes they disappear after a couple of weeks and come back in different places. Sometimes there will be none then sometimes I feel 2 or 3 different places. They are not tender and feel hard to the touch. I also feel like a dent in the back of my head. What could it be? Thanks! [/INST] Hi, dairy have gone through your question. I can understand your concern. You may have enlarged lymph node due to reactive hyperplasia, tuberculosis or lymphoma. Or you may have skin adnexal tumor or soft tissue tumor or some benign cyst like Desmond cyst. You should go for fine needle aspiration cytology or biopsy of that lump. It will give you exact diagnosis. Then you should take treatment accordingly. Hope I have answered your question, if you have any doubts then contact me at bit.ly/ Chat Doctor. Thanks for using Chat Doctor. Wish you a very good health. </s>