Neurofibromatosis Type 1 (von Recklinghausen disease) - one of the most common genetic disorders (prevalence: 1:3000) - mutation of the NF1 gene (chromosome 17): no control of cellular proliferation 50% positive family history 50% sporadic new mutations
Diagnostic Criteria for NF1 The patient should have two or more of the following: 1. Six or more cafe´ au lait spots 1.5 cm or larger in postpubertal individuals 0.5 cm or larger in prepubertal individuals 2. Two or more neurofibromas of any type or one or more plexiform neurofibromas 3. Freckling in the axilla or groin 4. Optic gliomas (tumor of the optic pathway) 5. Two or more Lisch nodules (benign hamartomas) 6. A distinctive bony lesion Dysplasia of the sphenoid bone Dysplasia or thinning of long bone cortex 7. First degree relative with NF1
Classification of Abdominal Neoplasms in NF1 Neurogenic neoplasms Neurofibroma Plexiform neurofibroma Malignant peripheral nerve sheath tumor Ganglioneuroma Neuroendocrine neoplasms Carcinoid Pheochromocytoma Paraganglioma / Gangliocytic paraganglioma Non neurogenic gastrointestinal mesenchymal neoplasms Gastrointestinal stromal tumor Leiomyoma / Leiomyosarcoma Embryonal tumors Rhabdomyosarcoma Neuroblastoma Wilms tumor Miscellaneous tumors Gastrointestinal adenocarcinoma Pancreatic adenocarcinoma Biliary adenocarcinoma The lifetime risk of developing an MPNST (malignant peripheral nerve sheath tumor) for a person with NF1 is 4-5%.
Neurofibromas are the hallmark lesion of NF1 65% asymptomatic 35% symptomatic: - palpable abdominal mass - pain along the distribuition of the nerve - GI mucosal involvement (hematemesis, melena, hematochezia) - intestinal obstruction (nausea, vomiting,abdominal distension) -bladder involvement (urinary frequency, incontinence, urgency, abdominal pain)
Radiologic features In the thorax, neurofibromas tipically appear as well- marginated, smooth, round or elliptic masses in the paravertebral regions or along the course of the vagus, phrenic, recurrent laryngeal or intercostal nerves. Plexiform neurofibromas are extensive fusiform or infiltrating masses that tend to surround mediastinal vessels with loss of normally visible fat planes. In the abdomen, neurofibromas are located in the paraspinal (symmetric or asymmetric masses within or adjacent to the psoas muscle) and presacral regions, along the course of the lumbosacral plexus. Mesenteric plexiform neurofibromas manifest as multiple nodules or infiltrating lesions of the wall of the intestine. The lesions in the perirectal region can infiltrate the perirectal fat and the pelvic structures.
US: heterogeneous in echotexture with variable through transmission (e.g. retroperitoneal and paraspinal neurofibromas), homogeneously or heterogeneously hypoechoic in echotexture (e.g. mesenteric neurofibromas) CT: neurofibromas are iso- or hypoattenuating masses, compared with adjacent soft tissue (20-25 HU on nonhenanced scans, 30-35 HU on intravenous contrast –enhanced scans). They have variable contrast enhancement and may calcify. MR: low signal intensity on T1-weighted images heterogeneous high signal intensity on T2-weighted images corresponds to areas of cystic degeneration or myxoid matrix
Primary bone malignancies (giant cell tumor, chordoma, lymphoma) or metastasis Primary or metastatic soft- tissue sarcoma
Imaging studies are indicated only when patients are symptomatic. Surgery is currently the only treatment option for most of the lesions in NF1. Chemotherapy and radiation therapy are recommended only for the treatment of the malignant tumors. Treatment
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