The invention relates to the use of a spongy material for producing an implant (10) utilized for occluding a cyst neck (3). In particular the polyvinyl alcohol Ivalon can be used as a spongy material. The invention further relates to a set of instruments for introducing such an implant (10) made of an spongy material into a cyst neck (3). Said set of instruments is composed of a puncture needle (5) for introducing a guide wire (6), a guide wire (6) whose distal end can be introduced into the cyst neck (3), an implant needle (7) comprising a connecting piece at the proximal end, a feeding unit (8) that can be joined to the implant needle (7) via the connecting piece, and the implant (10) which is made of spongy material and can be introduced into the cyst neck (3) via the feeding unit (8) by means of the implant needle (7). The inventive set of instruments can be used especially for the treatment of Baker's cysts.
