I take warfarin due to changed out mitral valve It has always been 13mg/day since 14 years ago when operated on. I have bruising side of my left breast with smallish lump that is little painfull. I had no impact, just played some golf. Mr Barry  Any ideas ?
This could potentially be muscle strain with associated inflammation from overuse and or repetitive movement. Alternatively, Warfarin necrosis of the breast is a rare complication yielding similar symptoms (though not identical) however these symptoms usually present days after Warfarin beginning. A white lump sounds to me as if it could be cyst-like; Cysts being a very common manifestation of the female Breast in general as individuals age and or reach certain age checkpoints. I would have a physical exam performed by ORGAN and or Primary Care Physician, explaining to them your symptoms and how the lump has come and changed in size and or consistency. From there they can pinpoint to you the likely diagnosis. I will also say that slightly painful is more often than not a good sign, if you are worried about cancerous potentialities. Nonetheless, a checkup would be the best recommendation. Many cysts come and go according to dietary and or hormonal causes; so really getting to the bottom of your habits with a physician will further help reach a diagnosis.