Should an Old Breast Implant Start to Show Its Port Under Skin/muscle?

This is very puzzling. You are correct. All ports should be removed and are typically intended for short term use of 6 months or less. A simple x-ray or ultrasound should leave no question about the possibilty of a port. These are very obvious. If there is any question, I would have it removed (implant +port) and replaced. Seek a consultation with a board certified plastic surgeon.

It sounds like you had breast reconstruction, and if so, your tissues are thinner than most people.  Palpability of the port is possible in thin patients.

It sounds as if the valve from the saline implant, which we use to fill the implant during surgery, is what is showing through your skin. I don't see any indication to biopsy your breast for this -- it will probably just rupture the implant.
It sounds as if you need to have the implant replaced. There are a number of excellent plastic surgeons in your area who could evaluate you for this. I recommend Dr. Adam Tobias in Brookline who has extensive experience with breast reconstruction as well. Good luck, /nsn.

It sounds to me like the port you are talking about is actually what we also call the valve on the saline implant itself. This was where the implant was filled, and can sometimes be felt under thin tissue. Some implants are filled with a remote port, under the skin nearby, usually to the side of the implant along your chest wall. That should be more obvious. Definitely see a plastic surgeon, because I have seen where an internist or even general surgeon will cause the patient anxiety by wanting to biopsy what is obviously (to a plastic surgeon) a fill port, or valve. You might also want to consider replacing your 10 year old implants. Silicone implants don't have fill ports, and usually make a nicer reconstructed result.

What you probably have is thinning of the tissues and may be feeling the valve of a saline implant under the skin. You should see a plastic surgeon to be sure that is what it is and consider changing to gel which doesn't have valves.