A tissue-separating catheter assembly comprises a rotatable shaft, having a distal shaft portion, and a tissue separator device extending along the shaft. The tissue separator device has a distal separator part at the distal shaft portion movable between a retracted state, towards the distal shaft portion, and an outwardly extending, operational state, away from the distal shaft portion. A localization device is movable to a radially expanded state. An expandable tubular element is movable so that its outer end is generally axially aligned with the localization device so to capture a separated tissue section therebetween to aid removal of the separated tissue section from the patient.