Map Active Directory Custom Properties with Office365

my company offers support to one of our clients and they use Office365.

The question is that they wanted to map custom properties from their Active Directory to Office365, so they could create custom properties at "User Profile Manager"

I searched on a few sites including Microsoft blogs and the most users told me that it is impossible to do at Office365. If we look in one of the properties in "User Profile Properties" we can see that there is a field (dropdown) for adding a new mapping but this field is empty. This field is the data connection but on Office365 there is no connection so I could select.

I wanted to know if is really possible to map active directory custom properties with Office365. We know our client already configured their Active Directory with Office365 so they can synchronize.

We used to do these things on a Sharepoint Server installation (On-Premisse) but in Office365 we can't.

Does anyone can give me a help?