554. Do we know everything about the effective multidisciplinary diagnostic and follow up procedures performed in patients with rare synchronous double cancers? An single-center case series analysis and review

Background: Synchronous cancer is an extremely rare in occurrence. It is characterized by the existence of two or more histologically distinct malignancies following each other in sequence by less than six months. In several studies the problematic aspects of the most effective creation and use of multidisciplinary diagnostic and follow-up procedures has been described. But it is also noted that there is a still a lack number of centers creating and systematically using an expanded criteria to avoid future misdiagnosis of unexpected multiple malignancy.