My right breast is paining a little and after doing self breast examination and consultation from general physician, I got to know that I have a small lump in the breast. Though the outer appearance of breast seems fine. And there is no pain as such. But while pressing hard a particular point near right side of nipple, I feel sharp pain. I am not pregnant and sexually inactive since past few months. I have been taking Isotetrinoin since past one and a half months for my acne. Can it be a side effect of that medicine?