A liner for use with a breast pump has an outer flange portion and a longitudinal portion extending outward from the outer flange portion. The outer flange portion has a first noncircular opening therein for receiving at least a portion of a breast including a nipple. The longitudinal portion has a second opening and a tubular passageway between the first noncircular opening and the second opening for allowing milk expressed from the breast received in the liner to pass through the liner. The outer flange portion is generally planar and adapted to engage a portion of the breast surrounding the nipple during use of the breast cup. The liner is configured for movement between an opened configuration of the noncircular opening and a collapsed configuration of the noncircular opening.
