Thanks for your question. Hyaluronic acid fillers such as Juvederm and Macrolane were previously used for non-surgical breast enhancement. However, their use has been discontinued. Some of the possible risks include:
• Infection. This usually occurs quite soon after the initial injections
• Displacement or migration of the injected filler. The gel may move to other untended locations. For example, below the inframammary fold.
• Persistent nodules that last for several years, beyond the expected lifespan of the filler. This is sometimes due to the formation of a capsule of scar tissue around the injected material.
• Difficulty with the interpretation of mammograms due to the formation of scar tissue
Although there isn’t any evidence that hyaluronic breast fillers such as Macrolane can cause breast cancer, the complications mentioned above may mask breast cancer, making it more difficult to detect and delaying the diagnosis. So although the lumps that you might find after filler injections are unlikely to be dangerous, it is safest to have these properly evaluated - this would involve a proper clinical examination and some form of imaging (ultrasound and / or mammogram).