If the tumor type is an aggressive one, ~10%-20% ulceration rate is feasible when tumors are >500 mm3; this is hard to avoid.
Some technique issues that could cause ulcerations are:
- Intradermal implanting. The xenograft should be s.c. implanted, it should be flexible and movable under the skin. If the xenograft implantation is fully or partially intradermal, it sticks to the skin and will invade the dermis, causing ulceration.
- Leakage: The cancer cells mixture may leak from the puncture after injection, which causes ulceration starting from the puncture. Use a small needle (27g or 30g) to avoid this. Hold the syringe for a few seconds, then pull out to let the xenograft get solid. Change the needle every 2-3 mice or more frequently. Wipe out leakage with a sterile cotton pad, and pinch the skin for a few seconds to stop leaking.
- To avoid leaking, keep the gel mixture on ice or let it solidify for longer before injection.