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UPDATE: My brave Mr BM went to see his GP this morning. GP seems to think it is absolutely nothing to worry about. The swelling in the inside leg he thinks is a varicose vein (so Sqad is on the money so far). However, as a precaution they are sending him for an ultrasound. GP said that they could operate if it continues to cause discomfort (and a cyst and varicose vein is all it is), but Mr BM nearly passed out at that point.