This is most commonly noted with above-the-muscle placement (not recommended for saline as there is much higher likelihood for ripple visibility and palpability, not to mention increased risk of capsular contracture from ductal bacteria biofilm on the implants), and very thin and small-breasted women (also a relative contraindication for saline implants because of the increased edge or ripple concerns).
I have had patients go so far as to note the filler port as a tiny "lump," see their physician, who orders a mammogram, and even schedules a consultation with a general surgeon for "possible breast biopsy," only to finally decide that since there is an implant in the breast they had better get the patient's plastic surgeon in the loop. I see the patient, have them examine the OTHER breast (the one nobody has been looking at since the "lump" is in the first-examined breast) and lo and behold, there's another identical "lump" that represents the palpable filler port. All worry and tests and time wasted for what should have been eliminated first by a visit to the plastic surgeon (in my case, also a fully-trained and American Board of Surgery-certified general surgeon before plastic surgery training).
I would also seriously consider both silicone gel implants and below-the-muscle placement for a more natural look, softer and more homogeneous (like breast tissue) "feel," and no risk of deflation requiring re-operation. There is also a much lower risk of visible or palpable rippling with silicone implants. Please see my article (on the About tab of my profile page on this site) titled: "Are Silicone Breast Implants Safe?" for more information, or click on the link below. Best wishes!