Case statement query

How can this be re-written. somehow not able to make it right. In case statement Then and ELSE are same would like to change it to single statement.

SELECT t.status_id status_id, ( CASE WHEN t .status_id NOT IN (SELECT status_id FROM firm_return WHERE enabled = ‘D’ and firm_id=t.firm_id)

THEN (cl.category_code + ‘-‘ + s.status_name) ELSE cl.category_code + ‘-‘ + s.status_name END) AS status_type FROM bla bla