Syndicate spokesman Ahmed Lotfi said at a press conference in Cairo on Tuesday that there were two doctors among those killed.
He added that 1,000 people, including 7 doctors, were injured.
Earlier in the day, Egyptian Ambulance Authority had said at least 51 people were killed and 435 were injured in the incident.
Also on Tuesday, pro-Morsi protesters staged a demonstration outside the Republican Guard barracks.
Since last week, Egypt has been the scene of rival rallies and clashes between thousands of supporters and opponents of the ousted president.
Morsi is reportedly being held “preventively” by the military. Senior army officials say he might face formal charges over accusations made by his opponents.
Several arrest warrants have been issued for the members of Muslim Brotherhood. Egyptian troops and security forces have recently expanded their roundup of top political figures from Muslim Brotherhood that had fielded Morsi for office.