[Involvement of the large intestine in neurofibromatosis type 1].

This report presents the cases of two female patients aged 54 and 57 years, both with colon involvement of type 1 neurofibromatosis. The first woman had a polypoid neuronal hyperplasia containing small Wagner-Meissner corpuscles, which had allowed identification of the neuronal nature of the lesion in a small mucosal biopsy specimen taken previously. The second patient had an idiopathic megacolon of the sigmoid, which had to be extirpated because of acute obstruction and ileus. Morphological examination revealed a typical plexiform neurofibroma of the bowel wall and neuronal hyperplasia of the colonic mucosa and submucosa, which had obviously caused disordered gut mobility leading to functional stenosis and extreme dilatation of prestenotic bowel parts. Gastrointestinal neurofibromatosis is rare and is characterized morphologically by neuronal hyperplasia of the mucosa and submucosa, sometimes containing small aggregates of ganglion cells by which it can easily be identified. However, in the majority of cases the increase of proliferating mucosal nerve fibres can only be confirmed by S-100 protein immunostaining. Furthermore, solitary, multiple and plexiform neurofibromas are found, but only the last, which arises from mesenteric or subserosal nerves, is virtually pathognomonic for neurofibromatosis. Gastrointestinal neurofibromas are usually late manifestations of the disease, but in exceptional cases they can be the initial sign of neurofibromatosis in patients who have no external stigmata that arouse suspicion. The occurrence of gastrointestinal neurofibromas should therefore lead to a careful search for other features of NF-1 in the affected patients and in their families.