1. A tissue marking apparatus, comprising: a marker introducer that includes a cannula and a stylet, the cannula having a lumen and a marker exit port, and the stylet being slidably received in the lumen, the stylet having a distal end; and a tissue marker configured to be received in the lumen distal to the distal end of the stylet, the tissue marker including: a marker portion configured to mark a site within a soft tissue mass, the marker portion having a length extending along a centerline of the marker portion between a first end and a second end and having a substantially continuous wall along the length, the substantially continuous wall bounding a hollow interior; and a drug-eluting portion comprising a drug, wherein the substantially continuous wall that bounds the hollow interior includes at least one opening configured to allow the drug to pass out of the hollow interior.