25 year old male with pain coming and going under armpit and down my arm and above collarbone?

? TOS: 20's male describes pain above clavicle, in armpit (intermittent), & down arm. Absent neck pain, this pain pattern suggests a neuropathy; likely related to impingement in region of brachial plexus. Thoracic Outlet Syndrome comes to mind. Neurology evaluation, nerve conduction studies, MRI, & ultrasound examination of the subclavian artery are some studies to help in making the diagnosis.