The invention relates to a coaxial cannula (1) for extracting samples fromtissue comprising abiopsy needle unit (9) provided with a space for sample extraction and asample separation unit(21) which coaxially encompasses the biopsy needle (9) on an external wall andis longitudinallymovable. The inventive coaxial cannula (1) comprises a sealing element (3)which is arranged onthe proximal end thereof and closes the space between the internal wall of thecoaxial cannulaand the external wall of the sample separation unit. Said coaxial cannula (1)is characterised inthat the sealing element (3) opens an air outlet when the biopsy needle unit(9) is inserted, andprevents air intake when the biopsy needle unit (9) is positioned and vacuumis produced in theinternal chamber of the biopsy needle.
