Brachytherapy seed insertion and fixation devices and systems to decrease implanted brachytherapy seed migration within tissue and minimize trauma. Component(s) with cavity or opening features are attached to a brachytherapy seed or series of seeds. The cavity or opening features interact with the patient's tissue to fix the seed and component assembly in place and inhibit movement/migration of the seed(s). The cavity or opening features may optionally be filled with an adhesive or other beneficial material. The seed(s) or seed and component assembly may be inserted using a delivery device having a needle through which the seed(s) or assembly are implanted and a stylet extending through the needle to cut tissue and facilitate insertion of the needle. The stylet has a reduced diameter cutting tip to cut a narrow hole in tissue, and a tapered region that stretches the narrow hole to accommodate insertion of the larger diameter needle.