<s>[INST] HelloI am a breast cancer survivor, right side 7 years ago.  Have noticed a hard lump on my collarbone, feels like hard bone and is the size of a large marble.  I have some night sweats but have had these for years. Also slight tingling around my mouth.  I also have a slight thyroid imbalance that is currently untreated, and suspected sjogrens.What are the causes of a lump on the collarbone.Had a mammogram about three months ago, and nothing showed. [/INST] HelloWelcome to Chat Doctor. Swelling in collarbone can be due to various reasons. It can be a bony swelling or enlarged lymph node. If it is bony swelling it is usually due to some benign bone disease, and you need not worry much for that. However since you are breast cancer survivor - chances of that swelling being a malignant lymph node are also high. Supraclavicular lymph nodes are located in that area and that can get involved in breast cancer. These lymph nodes are not seen in mammogram. You should consult your breast surgeon and undergo clinical examination. Ultrasonogram may be needed and biopsy will give you the final diagnosis. Regards </s>