You may notice lines running up from your armpits towards the back of the collar. And they are especially noticeable when you button your dress shirt all the way up. Gentlemen who have more developed trapezius muscles from weight lifting could face this issue more frequently.
Ideally, if you button your dress shirt all the way up most of the time, it should drape flatly across your upper chest without the lines nor puffs.
Increasing the shoulder slope on your dress shirt size will help to reduce the lines. Hence, it is important to choose a shoulder fitting that suits you best.
Changing the shoulder type setting for your fitting will change the elevation of the shoulders relative to the elevation of the back of the collar. A “Slope” shoulder type setting will be lower than a “Regular” which in turn will be lower than a “Flat”.