The rare Mondor disease is the formation of blood clots (thromboses) in the superficial veins of the breast. It may even more rarely occur in the penis, armpit or chest wall.
There is a sudden onset of pain and swelling of the skin over the affected area and a tender lump forms under the skin that is the blood clot in the vein.
It may be caused by an injury or infection to the area, but often no cause is identified.
The diagnosis is confirmed by an ultrasound scan. Other more serious causes of a breast lump must be excluded.
Treatment involves indomethacin or other nonsteroidal anti-inflammatory medications, hot packs and pain relievers. The problem settles spontaneously over a week or two.