PB2044: TRIAL IN PROGRESS: OBSERVATIONAL STUDY IN PATIENTS WITH ADVANCED SYSTEMIC MASTOCYTOSIS TREATED IN ITALY WITH MIDOSTAURIN (OVIDIO). (23rd June 2022) - Grifoni, F. I.; Mannelli, F.; Papayannidis, C.; Triggiani, M.; Bini, R.; Valsecchi, D.; Zanotti, R.