ANTICANCER RESEARCH 25: 1699-1702 (2005)

Malignant Peripheral Nerve Sheath Tumors (MPNST) in Neurofibromatosis Type 1 (NF1): Diagnostic Findings on Magnetic Resonance Images and Mutation Analysis of the NF1 Gene

REINHARD E. FRIEDRICH1, LAN KLUWE2, C. FÜNSTERER3 and V.F. MAUTNER4

1Maxillofacial Surgery Clinic and 2Laboratory for Tumor Biology and Developmental Disorders, Maxillofacial Surgery Clinic, Eppendorf University Hospital, University of Hamburg; 3MRI-Institute, Hamburg-Othmarschen; 4Department of Neurology, Klinikum Nord, Hamburg, Germany

Abstract. Plexiform neurofibroma (PNF) is a typical feature on 50 patients with NF1 and nerve sheath tumors, of whom 7 of neurofibromatosis 1 (NF1). About 10% of patients with NF1 had atypical pain, tumor growth or neurological deficits develop malignant peripheral nerve sheath tumors (MPNST), indicative of malignancy; the other 43 were asymptomatic. On usually arising from PNF, and this is the major cause of poor MRI, all 7 symptomatic patients had inhomogeneous lesions, prognosis. A better prognosis can be achieved if the tumors are due to necrosis and hemorrhage and patchy contrast diagnosed at an early stage. Our objective was to establish enhancement. In one patient, the multiplicity of confluent magnetic resonance imaging (MRI) criteria for MPNST, and to tumors with inhomogeneous areas in addition to central lesions test their usefulness in detecting early malignant changes in did not allow the exclusion of malignancy. Only 3 of the 43 PNF and to correlate the findings with the mutations of the asymptomatic patients had comparable changes; the other 40 NF1 gene. Patients and Methods: NF1 outpatients were patients had tumors of relatively homogeneous structure on T1- diagnosed according to the NIH criteria. All patients underwent and T2-weighted images before and after contrast a complete dermatological, ophthalmological and neurological enhancement. All 3 asymptomatic patients with inhomogeneous examination and ultrasound of the abdomen between 1997 and lesions were shown to have MPNST. Analysis of mutations of 2002. The study was approved by the Institutional Review the NF1 gene of the 10 MPNST patients revealed a variety of Board and all patients gave informed consent to analyze clinical mutations. Concerning the correlation of genetic findings and records and tumor material for scientific purposes. MRI was MPNST in NF1, the sample size of this study group was too performed with devices at 1.5 Tesla field strength (Siemens small to define genotype-phenotype relations. In this cohort, all Magnetom Symphony) or in some patients at 1.0 Tesla field types of mutations were found. Conclusion: This study provides strength (Siemens Impact Expert). T1- and T2-weighted evidence for certain radiographic findings on MRI in PNF of sequences including STIR-sequences were acquired. Ultra-rapid NF1 patients that have to be considered as signs of malignancy, image sequences with HASTE technique were performed for in particular indicating an MPNST. These findings are trunk imaging. In patients with no contraindication for the especially valuable in the long term follow-up control of patients application of contrast media, Gadolinum-DTPA Magnevist with large tumors (plexiform neurofibromas). was administered intravenously. Results: MRI was performed Neurofibromatosis 1 (NF1) is an autosomal dominant disease with an incidence of about 1 in 3,500 humans. NF1 is caused by mutations of the NF1 tumor suppressor gene Correspondence to: Prof. Dr Reinhard E. Friedrich, Maxillofacial (OMIM 162200) located on chromosome 17q11.2 (2, 20). Surgery Clinic, Eppendorf University Hospital, University of Hamburg, NF1 patients can develop a plethora of signs and symptoms. Martinistr. 52, D-20246 Hamburg, Germany. Tel: 040-42803-3259, Fax: Benign and malignant lesions like neurofibromas, pilocytic 040-42803-8120, e-mail: [email protected] astrocytomas and malignant peripheral nerve sheath tumors Key Words: Neurofibromatosis, neurofibromatosis type 1, (MPNST) characterize NF1 as a disease with increased risk malignant peripheral nerve sheath tumor, MPNST, mutation, of tumor development. Indeed, the development of tumors magnetic resonance images. in NF1 follows the two-hit model for a tumor suppressor

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Table I. Patients, growth types of plexiform neurofibroma, follow-up following treatment of MPNST, and mutation of the NF1 gene. Patient No. 8 experienced 2 synchronous MPNST. DED = deceased with evidence of the disease; NED = no evidence of the disease.

Number Age Localization Growth Type Growth Pain Neurological GradeCoindre Follow-up Mutation (years) of Plexiform Deficit at Neurofibroma/ Diagnosis MPNST

1 19 Limb Displacing Yes Yes No 2 2 Alive Non-sense (Exon 37) 2 21 Trunk Displacing No No No 2 3 Alive Not found 3 20 Trunk Invasive No No No 2 2 DED Not found 4 24 Trunk Invasive Yes Yes No 2 2 DED Frame shift (Exon 20) 5 30 Trunk Displacing Yes Yes No 2 2 DED Non-sense (Exon 27a) 6 31 Limb Displacing Yes Yes No 2 2 DED Missense (Leu>Pro, Exon 18) 7 35 Limb Invasive Yes Yes Yes 2 3 DED Deletion 8 35 Trunk & Limb Invasive Yes Yes Yes 2 2 DED Non-sense (Exon 10a) 9 13 Limb Invasive Yes Yes Yes 3 3 DED Frame-shift (Exon 21) 10 56 Limb Invasive No No No 2 2 Alive, NED Non-sense (Exon 36)

gene (13). Somatic loss or mutation of the normal NF1 allele has been found in different tumor entities of NF1 patients, e.g. cutaneous or plexiform neurofibromas (PNF), pilocytic astrocytomas and MPNST (3, 17-19, 14, 8-12). MPNST are highly aggressive neoplasms of Schwann cell origin. It is assumed that about 50% of all MPNST develop in NF1 patients. The life-time risk of developing a MPNST is 8 – 13% among NF1 patients, with a 5-year survival rate of only 21% (5). MPNST are a leading cause of death in NF1 patients (16). This entity responds poorly to chemo- or radiotherapy, with surgical ablation with wide resection margins being the only effective therapeutic option (21). A recently published study on NF1 patients suggested that those patients with a megabase deletion of the entire NF1 locus develop a MPNST more frequently than NF1 patients with other kinds of constitutional mutations (4). Wu et al. (22) presented 7 NF1 patients with MPNST, of whom 3 patients had constitutional mutations and 3 had deletion of the whole NFI gene. In this study, we compared the constitutional NF1 gene mutation with MRI findings. The aim of this study was to compare the mutation type of MPNST and the appearance of these tumors on magnetic resonance imaging (MRI) scans in order to find out whether the types of mutation correlate with the image of the tumors. Figure 1. NF1-patient No. 10. The PNF of the left lower limb had existed for decades. MRI reveals inhomogeneous, ill-defined lesions inside the Patients and Methods extensive tumor. The resected tumor proved to be a MPNST invading the adjacent muscles. Limb amputation was carried out. Three years after MRI. MRI was at 1.5 or 1.0 Tesla, with T1- and T2-weighted surgery, the patient is alive with no evidence of MPNST. sequences including a short-Ù inversion recovery (STIR)

1700 Friedrich et al: Diagnosis of Malignant Peripheral Nerve Sheath Tumors in NF1 sequence. Ultra-rapid half-Fourier single-shot turbo spin-echo Discussion (HASTE) sequences were used for imaging of the trunk. Intravenous contrast medium was administered in patients with Patients with NF1 who develop a MPNST have different no contraindication. Ten patients were investigated with MPNST mutations of the NF1 gene but share some characteristic and NF1. Seven of these patients presented with pain, tumor findings that can be identified on MRI. In this small cohort, growth or neurological deficit. The malignant tumor of 3 patients was an incidental finding and diagnosed by recently published MPNST in NF1 patients frequently showed inhomogeneous radiological criteria (15). contrast enhancement. This inhomogeneity correlated to regions of necrosis and hemorrhage alternating with areas Genetics. The 10 patients included in this study were examined in of solid tumor. This correlation was proven macroscopically the NF outpatient clinic in Hamburg. All patients were suffering during tumor surgery and on histological sections of from NF1, diagnosed according to the updated NIH criteria (7). resection specimens, in particular on the preparations of 2 The investigation protocol was approved by the local ethics amputated limbs of 2 of our patients. Interestingly, in 3 committee, and all patients provided informed consent. All patients underwent MRI of the brain, the region of interest, patients the MPNST was detected in the PNF on follow-up ultrasound of abdominal organs, ophthalmological investigation MRI, even though the patients did not have significant and neurological investigation. MPNST was revealed from clinical features. The diagnosis was made from changes on biopsies or resection specimens. the images, in particular the new findings of inhomogeneous DNA was extracted from blood lymphocytes using a QIAamp contrast enhancement areas inside the (large) PNF. Blood Kit from Qiagen (Hilden, Germany). Mutation analysis was performed by direct sequencing of 57 constitutive NF1 exons Conclusion (6, 10, 12). Primers for exon 12b were designed in this study. Several primers were from Abernathys et al. (1) and Fahsold et al. (6). All mutations were confirmed by repeat amplification and MPNST in NF1 share some findings that can be used for sequencing (12). differential diagnosis in follow-up controls, in particular in those patients with large tumors. The mutations of the NF1 Morphology. For patients 1 and 8, an amputated limb was available gene varied considerably and showed no predilection for any for macroscopic investigation. The correlation of MRI images and type. However, in larger series megabase deletions were macroscopic and microscopic findings was carried out on these found to be significantly associated with MPNST in NF1 (12). specimens. Immunohistochemical and light microscopic studies were performed on formalin-fixed, paraffin-embedded tissues. Diagnosis was based on the light microscopic features of cellularity, Acknowledgements mitotic rate, size of necrotic areas, nuclear pleomorphism and the presence of rhabdomyoblasts. Histological grading was determined This study was supported by Hamburger Stiftung zur Foerderung according to the National Cancer Institute (USA) system and der Krebsbekaempfung (Grant No. 161), Hamburg, Rudolf- tumor differentiation was scored according to histological type in Bartling-Stiftung, Hannover, Deutsche Krebshilfe (Grant No. 70- the updated version by the Fédération National des Centres dé 2794-De 1), Bonn, and Deutsche Forschungsgemeinschaft (FR Lutte Contre le Cancer. 1035-6/1), Bonn, Germany.

Results References

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