Topical hydrocortisone cream is mainly used for the treatment of hives or other allergic reactions of the skin (e.g. eczema).

However, is it safe to use hydrocortisone cream on hives or eczema in case the skin of these areas is broken/open (e.g. because of scratching) ?

It turns out that it is definitely safe. In fact, it seems that in case of infected wounds, the use of hydrocortisone can be beneficial, while in teh case of uninfcted wounds hydrocortisone seems to make healing slower.

References:
http://www.ecolife.nl/polysaccharide.htm
http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1515458&blobtype=pdf