Foster, 51, posted an Instagram of herself wearing only a towel Friday to demonstrate three areas along her chest where her doctor found silicone that had leaked out after her boob job.
"Turn a mess into a message," she captioned the snapshot. "We might have hit the jackpot by finding all this silicone from a 20 year old implant rupture through ultrasound mapping as shown in this selfie. Thank you Dr.Feng for holding my hand and leading the way."
If silicone breast implants rupture, they can cause pain, soreness and swelling, though experts don't believe the problem results in grave illnesses like breast cancer, according to the Mayo Clinic.
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Foster has stayed positive throughout her fight against Lyme, which has affected her brain function, including her ability to read and write.
"The most frustrating thing is that there is medical data on Lyme and spirochete infections going back all the way to 1908, but yet we still don't have proper diagnostic testing, a vaccine, or a cure for Lyme disease while we are living in the United States of America, the most extraordinary country in the world," Foster wrote in a blog post in January. "Something doesn't add up here, and I will make it my life mission to figure this out, because nobody deserves to suffer this way in 2015."