Hi Angela, It s unlikely that a blot clot would present with a lump under the rib cage. This sounds like a hematoma (blood clot under the skin). This may be due to the blood thinners themselves, as this often causes easy bruising. I d recommend he treat himself with warm compresses, which should help the hematoma reabsorb. The symptoms of a blood clot in the lungs usually don t have any outward signs, but the patient themselves will have shortness of breath and difficulty breathing. I wouldn t worry too much about this finding, but if it doesn t resolve within a few days or isn t improving, then I d have him see his doctor and an ultrasound of this mass can help to see what it is. But this doesn t sound like a clot in the lungs at all. I hope this is helpful. Please feel free to contact me if you have any further questions.