Hello Thanks for writing to us with your health concern. No, this cannot be a build up of stools. They would not come out and form a lump like this, even if you are constipated. THis is most probably a lymphocele. Owing to the radiation, the lymph vessels get thrombosed and blocked. Lymph gets collected forming a lymphocele. ANother possibility with the history of endometrial cancer is that this could be a lymph node. Please do not ignore it. IT could also be another separate discrete vulval swelling. IN view of previous history of cancer, do not delay consultation. Dont worry , it is most likely to be something benign. All the best. Take care.