What are "sys.extended_index..." indexes? A CHECKDB run reports corruption in sys.extended_index_1066482673_384000. What kind of index are represented by the name pattern sys.extended_index_...? The message is:


  The spatial index, XML index or indexed view 'sys.extended_index_1066482673_384000' (object ID ...) does not contain all rows that the view definition produces.  This does not necessarily represent an integrity issue with the data in this database. For more information about troubleshooting DBCC errors on spatial indexes, XML indexes, and indexed views, see SQL Server Books Online.
Extended Indexes are full text indexes, XML indexes, and Spatial indexes.  Reason, the 3 types of indexes are better handled outside the B+ tree index.

I know you do not care to correct this but, did you recently upgrade?  Try changing the compatibility level if it's not SQL Server 2014 and run CHECKDB again

You can identify the table object for the extended index error by using the below code. You may need to tweak the name in the where clause if I have it wrong.

SELECT 
    OBJECT_NAME(PARENT_OBJECT_ID) AS table_object,
    name,
    create_date
FROM sys.internal_tables it
WHERE INTERNAL_TYPE = 207
AND it.name = 'extended_index_1066482673_384000'


Hope this helps!