Staging pressure ulcers

I just returned to nursing after being out for 5 years and I am feeling a little rusty when it comes to some assessment skills. I had a patient with a pressure ulcer on her heel. I am confused as to the stage. It is 6.8cm x 4cm and is open. The wound bed is yellowish/white which looks like slough to me. The confusing part is that it is not deep at all, it looks superficial so I'm not sure if it would be stage II or III. Does it have to be deep to be stage III? Can a stage II have slough? Or is it unstagable?
there are plenty of websites with good information on staging. The best tip I can give is that you are staging the wound bed, not the outer edges. So if the bed is not open skin, it is a I. Open skin is II. Open skin down to fascia is III and to bone is IV. If you cannot see the bed (covered by eschar, pus, etc) then it is unstageable. HOWEVER, I am not a wound care nurse, so I still recommend you check out the various websites by wound nurse associations, etc. WWW.medline.com has courses on pressure ulcer treatment and prevention.

Okay, thank you!

Here is a pressure ulcer module from NDNQI: https://members.nursingquality.org/N...UlcerTraining/