Figure 11a. Plexiform neurofibroma of the rectosigmoid colon in a 5-year-old girl with a 3-year history of constipation and previously unrecognized NF1. (a) Coronal T1-weighted MR image shows a thick hypointense thickening of the rectal wall. (b) Axial T2-weighted MR image shows a ringlike pattern (black arrows) to the hyperintense plexiform neurofibroma. The tumor also encircles the vagina and urethra. A plexiform neurofibroma of the left sacral plexus is also present (white arrow). (c) Photograph of the resected specimen shows the nodular cut surface of the plexiform neurofibroma that arose from the rectal wall.