They are signs they need for potting up,Marcello..and are drawn towards the light ..you should do them as soon as possible..just check the tubers first,for any signs of softness or mould..after winter storage..cut off any that are soft...keep them somewhere warm and bright..

Your cool dark shed is obviously not that cool :)
I would plant the tubers in trays or pots, depending on the size, and keep them somewhere that gets plenty of light.
If the shoots are that long i would cut them back to where they join the tuber, as if you were taking cuttings. Fresh shoots will appear from there that will grow normally and be ready to plant out end of May.