<s>[INST] My 14 yr old son just found a hard lump just below his right collar bone, on his breast bone or rib cage area?   no pain involved, but it is about the size of a fifty cent piece...very athletic boy but doesnt remember hitting that area recently...your best guess?? [/INST] Hi, Welcome with your query to Chat Doctor virtual Clinic. I reviewed all the details of your query, in context of the painless hard lump below right collar bone. Based on the facts of your query, You seem to have Costco Chat Doctor. You don't have history of any recent viral/bacterial infection in the area around it and hence no question of it being lymphadenitis there. Being athletic, the only possibility is Costo-chon </s>