Disseminated neoplasia in flat oysters Ostrea edulis from Galicia (NW Spain): Occurrence, ultrastructural aspects and relationship with bonamiosis

► The ultrastructure of neoplastic cells of Ostrea edulis is characterised. ► Oyster disseminated neoplasia is influenced by oyster age and shows seasonality. ► Geographic origin influences oyster susceptibility to disseminated neoplasia. ► Association between disseminated neoplasia and bonamiosis was detected.