My TOS was diagnosed independently by first a chiro and then later a vascular MD. My pec minor syndrome is self diagnosed based on three things:

1) The paragraph "In 2005 we became aware of a large number of patients who, in addition to these symptoms, also had pain in the anterior chest wall, just below the collar bone along with pain over the shoulder blade and in the arm pit. Until recently it was thought that these symptoms were due to TOS, but now it has been learned that they are due to a condition frequently accompanying TOS, namely pectoralis minor syndrome." at http://www.ecentral.com/members/rsanders/ matches my symptoms

2) My PT has found my pec minor on the symptomatic side is tight. (She also agreed with pec minor syndrome when I showed her the above paragraph.)

3) When I do pec minor stretches, I can feel the one on the symptomatic side is abnormally tight. Almost like it "catches".