A breast implant system comprises at least one casing (3, 4) with a flexible outer shape for implantation in a patient's body so as to form part of a breast implant (10) and further comprises at least one first element (1) contained in the casing and optionally at least one second element (2) also contained in the casing. The first and second elements are either displaceable within the casing and/or their volume can be changed in order to change the shape and/or size of the breast implant. A reservoir (R) comprising a lubricating fluid is connected to the casing so as to allow lubricating fluid to be supplied to and removed from the casing in order to reduce surface friction between adjacent elements and/or between the casing and the elements before the shape of the breast implant is changed.
