Cancerous

Some people have suggested that the minor irritation and foreign substance of body piercing and implants could lead, in the long term, to an increased risk of cancer in the modified area. While there may be fictional theoretical anecdotes illustrating this, there is no evidence supporting this theory.

In fact, virtually all legitimate studies have shown not only no increase in cancer rates, but have actually indicated a decreased risk of cancer from procedures such as breast implants. This decrease is believed to be in part from the slightly enhanced immune system response due to the foreign body, and in part from the pressure of the implant limiting blood flow to the potential tumors (which are very oxygen-hungry). It is not unreasonable that the same would apply to some smaller extent with smaller implants.

Note: Certain components of stainless steel alloy indeed are carcinogenic and/or mutagenic (specifically nickel and chromium).