Figure 10b. Plexiform neurofibromatosis of the colon in a 9-year-old boy with previously unrecognized NF1 who was being evaluated for an asymptomatic palpable abdominal mass. (a–c) Intravenous contrast-enhanced CT scans (obtained at successively lower levels) show mural thickening (arrows) of the transverse (a), descending (b), and rectosigmoid (c) colon. (d) Photograph of the opened resected colon shows the complex, tortuous, "wormlike," plexiform neurofibromas (arrows) expanding the submucosal layers of the colonic wall.