Hard lump under left side of collarbone and slightly to the left of sternum clavicular bone = what are possible causes of this? thank you.

Any weight loss: early satiety? decreased appetite? see your primary care doctor to schedule and upper endoscopy, chest x-ray. Have any other symptoms such as upper respiratory infections? How large is the lump, how long has it been there. Any lump ( lymph node???) on the side of your left collarbone is known as virchow's node.. This lymph node drains your thoracic ducts, your abdomen and your thorax.