Shopping API returned the following node as part of the item data, it's also available in GetSingleItem.
<PrimaryCategoryName>Clothing, Shoes & Accessories:Men's Clothing:Blazers & Sport Coats</PrimaryCategoryName>
<SecondaryCategoryName>Clothing, Shoes & Accessories:Men's Clothing:Coats & Jackets</SecondaryCategoryName><SecondaryCategoryIDPath>11450:1059:57988</SecondaryCategoryIDPath>
It would be very useful to have this data available in the Finding Response
This can be used among other things, to build bread crumbs or link to parent categories without making additional calls or building a supporting database.
It's directly useable on an item level as well, something that is lacking with the CategoryHistogram.