Two Separated Ileal Adenocarcinomas in Neurofibromatosis Type 1 A B Fig. 5. (A) Diffuse transmural neurofibroma and overlying tubular adenoma of small bowel (hematoxylin-eosin, original magnification × 100). (B) Adenocarcinoma arising from tubular adenoma (hematoxylin-eosin, original magnification × 200). A B Fig. 6. (A) Tubular adenoma glands resembling colitis cystica profunda (original magnification × 40). (B) Prominent ganglion cells in the mucosa (original magnification × 400). In the smaller mass, the well differentiated adeno- carcinoma was confined to the mucosa (Fig. 5B). The intervening edematous elevated lesion between the two polypoid masses showed a multifocal tubular adenoma with transmural neurofibromatous stroma. The mucosal tubular adenomatous glands extended into the submucosa without cytologic and structural atypism, resembling colitis cystica profunda (Fig. 6A). Each area of the involved ileal segment showed variable histological severity of neurofibromatosis. In the fully developed area, the mucosa showed individual and grouped ganglion cells with the background of neurofibromatosis (Fig. 6B). The muscularis mucosa was indistingui- shable due to the proliferating neurofibromatous stroma. The ganglion cells were made more prominent in the immunohistochemical study by utilizing the S-100 protein, synaptophysin, and neuron specific enolase antibodies. The sub- mucosa showed wavy spindle cell proliferation, with scattered mast cells, eosinophils, and some giant cells. This is similar to the findings in an inflammatory fibroid polyp. The muscle layers were split by intervening wavy spindle cells, which were accentuated with masson-trichrome stain. These cells were positive for S-100 protein and neurofilament antibodies, but negative for c-kit antibody. The intermuscular Auerbach plexus was hyperplastic, with a band-like structure, and the serosa showed many conglomerated nodules composed of wavy spindle cells. In the less developed area, we observed more nodular lesions rather than diffuse neurofibromatous proliferation. The appendiceal mucosa was atrophied, with diffuse neurofibromatous stroma in the submucosa and muscle layers. The colon showed mildly hypertrophied nerve fibers without NF stroma. We performed a genetic study for the ras Yonsei Med J Vol. 48, No. 6, 2007