I would go with dissection of a package of obturator lymph nodes for pathology. Although your MRI and PET may indicate everything is contained as mine did, my Surgeon did use real time pathology during surgery and was surprised when margins came back positive when everything would have inferred they would not. He then needed to continue my surgery for additional two hours carefully removing more margin and my final post surgery pathology was negative margin. He took out one set of lymph nodes which were negative.