Under the hospital's system, technicians scanned tests and flagged any that looked abnormal. Officials said it appeared that unflagged tests were set aside and forgotten.
That system is not used at other city hospitals.
The Health and Hospitals Corporation acknowledged the problem after The New York Times asked about it. It said the patients will be notified and told if they need follow-up treatment.
HHC said one doctor was fired and another was demoted.
