DEVICES AND METHODS FOR PERFORMING PROCEDURES ON A BREAST

1 - 16 . (canceled)

17 . A device for cutting tissue having a bowed cutting element, comprising:

a shaft having a central axis; and

a tissue cutting element coupled to the shaft, the tissue cutting element being movable from a collapsed position to an expanded position, the cutting element bowing outwardly when in the expanded position, the cutting element moving generally in a first plane when moving between the collapsed and expanded positions;

the shaft having a first thickness and a second thickness relative to the central axis of the shaft, the first and second thicknesses lying in a second plane which is generally parallel to the first plane, the second thickness being at least 1.25 times larger than the first thickness and the side of the shaft having the second thickness leading the cutting element during rotation.

18 . The device of claim 17 , wherein:

the second thickness is at least 1.5 times larger than the first thickness.

19 . The device of claim 17 , wherein:

the tissue cutting device has a tissue collection element which holds the tissue volume cut free from the surrounding tissue.

20 . A device for cutting tissue using a bowed cutting element, comprising:

a shaft; and

a tissue cutting element coupled to the shaft, the tissue cutting element being movable from a collapsed position to an expanded position, the cutting element bowing outwardly when in the expanded position, the tissue cutting element moving generally in a first plane when moving between the collapsed and expanded positions;

wherein the shaft is at least 1.25 times thicker on a leading side than on a trailing side, the thickness being measured along a second plane perpendicular to the first plane, the cutting device being rotated during cutting so that the leading side leads the cutting element.

21 . The device of claim 20 , wherein:

the shaft is at least 1.5 times thicker on the leading side than on the trailing side.

22 . The device of claim 20 , wherein:

the shaft is thicker on the leading side adjacent to the cutting element and is substantially the same as the trailing side at substantially all other parts of the shaft.

23 . A method of cutting tissue using a bowed cutting element, comprising the steps of:

providing a tissue cutting device having a shaft and a tissue cutting element coupled to the shaft, the tissue cutting element being movable from a collapsed position to an expanded position, the cutting element bowing outwardly when in the expanded position, the tissue cutting element moving generally in a first plane when moving between the collapsed and expanded positions, wherein the shaft has a first and second thicknesses lying in a second plane which is generally parallel to the first plane, the second thickness being on a side of the shaft from which the tissue cutting element expands, the second thickness being at least 1.25 times larger than the first thickness;

introducing the tissue cutting device into tissue;

expanding the tissue cutting element toward the expanded position;

rotating the tissue cutting device so that the cutting element moves through the tissue to cut the tissue, the cutting device being rotated in a direction in which a side having the second thickness leads the cutting element during rotation;

moving the tissue cutting element back toward the collapsed position to cut a tissue volume free from the surrounding tissue.

24 . The method of claim 23 , wherein:

the providing step is carried out with the second thickness being at least 1.5 times larger than the first thickness.

25 . The method of claim 23 , wherein:

the providing step is carried out with the tissue cutting device having a tissue collection element which holds the tissue volume cut free from the surrounding tissue.

26 . The method of claim 23 , wherein:

the providing step is carried out with the shaft having at least the second thickness adjacent to the cutting element.

27 - 72 . (canceled)