Here's what I found when I looked into the matter and what I did as a result: On my PC the Office file cache contained over 25,000.
In such a configuration the Microsoft Office file cache can grow to be HUGE, tens of thousands of files occupying tens of gigabytes (there are many complaints in Windows support forums about this profligate usage of disk space). My main Windows 10 PC runs Microsoft Office 2013, OneDrive, and the Office Upload Center.