Protruding Vein Under Left Armpit

I have found what I thought was a lump under my left armpit. Then I realized I have a protruding vein all the way down my left armpit. Occasional shoulder pains. Headaches daily. I have high incidence of Diabetes in my family, genetic high cholesterol, and have undergone a complete thyroidectomy.
Is any of this related? Would blocked arteries cause protruding vein in the left armpit?