Hi Tanyar, I had a large haematoma (blood clot) form 3 weeks after my mastectomy and insertion of tissue expanders. This happened spontaneously, and didn't hurt, but the whole area became distorted and hard very quickly. Eventually as the bluish colour of the clot became obvious. This required surgery to removed the expander and wash out the clot. 800mls was drained out. If the area has gone hard, and painful, I would suggest taking the advise of the breast care nurse and seeing your surgeon. It might be a build up of fluid or old blood, which in itself can be very uncomfortable, but it might also be an infection which could be painful and may require antibiotics. Certainly your surgeon or even a GP should be having a look at it, so as to put your mind at rest. Good luck. Love Chris xx