Plexiform Neurofibromas (WHO grade I) are Neurofibromas which are elongate and multinodular, formed when the tumor involves either multiple trunks of a plexus or multiple fascicles of a large nerve, such as the sciatic. Some Plexiform Neurofibromas resemble a bag of worms, others produce a massive ropy enlargement of the nerve. (Adapted from WHO.)
