I-485 returned from department of state to TSC, what does it mea

Dear xiao baitu and other professionals:

I got a notice from TSC:

This is to advise you that we have received the above application or pttition back from the Department of State, along with their request that it be reviewed. We will notify you of any action we take on this case.

my question: why my case went to the Department of State? Do all I-485s have to go through Department of State before approved?

Very confused, hope to get some help to figure out what is going on, many many thanks.