How can I use nested cases in mySQL?

I want to work with nested cases:

SELECT *, 
    GROUP_CONCAT(DISTINCT CONCAT(
    CASE
      WHEN data.name NOT "field" THEN   
        CASE
          WHEN data.category = "A" THEN "A"
          WHEN data.category = "B" THEN "B"
          ELSE "C"
        END,data.name
    END
   )ORDER BY FIND_IN_SET(data.category,"B,C,A") ASC, data.name ASC SEPARATOR " <br>") AS result
  FROM data;');

But I get an error message:

Fatal error: Uncaught PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'data.name END ' at line 11