Plexiform Neurofibroma

Diagnosis

Plexiform Neurofibroma

Diagnosis

Plexiform Neurofibroma

History

NF1 patient with right lower extremity mass.

Findings

FDG PET/CT demonstrates a 6.7 x 6.9 x 12 cm hypermetabolic lesion involving the right sciatic nerve.Magnetic Resonance Imaging shows an hyperintense T2 lesion, with Gadolinium Enhancement measuring 6.3 x 7.4 x 13 cm.Biopsy showed no evidence of malignancy but the presence of a cellular neurofibroma with positivity for S-100 , SOX-10 and NF200.

Discussion

Neurofibromatois 1 (NF1) is a genetic syndrom in which mutations in the neurofibromin 1 gene yields to the production of non-functional neurofibromin. Normal neurofibromin acts as a tumor suppressor , regulating RAS proteins, the later ones being responsible for cell growth, survival and differentiation. Other RASopathies and related disorders with dysregulation of the Ras Mitogen-activated protein kinase signaling pathway include Noonan syndrome, Neurofibromatosis type 2, Legius syndrome and schwannomatosis.
Patients with NF1 will develop multiple types of lesions due to overgrowth. Among them, the typical Café-au-lait lesions and Lisch nodules, benign growths in the iris .
Involvement of the soft tissue includes localized and diffuse cutaneous neurofibromas, vsiceral neurofibroma and plexiform neurofibromas (PN) . Those latter lesions are characterized by growths along multiple nerve bundles, some becoming quite large with subsequent symptoms due to compression of normal structures.In patient with NF1, the risk of developing malignant peripheral nerve sheath tumor (MPNST) from PN is around 10 percent. NF1 patients are also at risk of optic gliomas, gastrointestinal stromal tumors, pheochromocytoma, juvenile myelomonocytic leukemia.Intermediate between PN and MPNST, atypical neurofibromas (ANF) demonstrate more cellularity and fascicular component than PN but no atypia or mitotic activity when compared to MPNST. However, they are considered as precursors of MPNST.One study evaluated the FDG avidity of ANF and almost all lesions demonstrated SUVmax superior to 3.5. In the subgroup of patients with prior FDG PET/CT, lesions ' s SUVmax had increased in 72 percent of them. Finally, during follow-up, some ANFs transformed into MPNST.

Key points

Differential Diagnosis.
Schwanoma.
Malignant Peripheral Nerve Sheet tumor. Plexiform Neurofibroma.

References

The Diagnosis and Management of Neurofibromatosis Type 1. KI Ly et al. Med Clin N Am 2019;103:1035-1054
Evaluation of 18fluorodeoxyglucose positron emission tomography (18FDG PET) in the detection of malignant peripheral nerve sheath tumours arising from within plexiform neurofibromas in neurofibromatosis 1. R E Ferner et al . J Bingham. J Neurol Neurosurg Psychiatry 2000;68:353–357
[18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) as a diagnostic tool for neurofibromatosis 1 (NF1) associated malignant peripheral nerve sheath tumours (MPNSTs): a long-term clinical study. R. E. Ferner et al. Annals of Oncology 19: 390–394, 2008
The role of [18F]-fluorodeoxyglucose positron emission tomography in predicting plexiform neurofibroma progression. MJ Fisher et al . J Neurooncol 2008; 87:165–171
The role of [18F]-fluorodeoxyglucose positron emission tomography in predicting plexiform neurofibroma progression. J Michael . J Neurooncol 2008; 87:165–171
[18F]-Fluorodeoxyglucose positron emission tomography in children with neurofibromatosis type 1 and plexiform neurofibromas: correlation with malignant transformation. L. L. Tsai. J Neurooncol 2012; 108:469–475
Chapter 17 Peripheral Nerve Sheath Tumors: Diagnosis Using Quantitative FDG-PET
E Shurell et al. M.A. Hayat (ed.). Tumors of the Central Nervous System, Volume 4, 161 DOI 10.1007/978-94-007-1706-0_17, © Springer Science Business Media 2012
Evaluation of F18-deoxyglucose positron emission tomography (FDG-PET) to assess the nature of neurogenic tumours. S. Cardona. EJSO 2003; 29: 536–541
Value of PET in the Assessment of Patients with Neurofibromatosis Type 1.
MA. Bredella et al . AJR 2007;189:928-935
Review Article Usefulness of Whole-Body Fluorine-18-Fluorodeoxyglucose
Positron Emission Tomography in Patients with Neurofibromatosis Type 1: A Systematic Review. G et al. Radiol Res Pract 2012
Intérêt de la tomographie par émission de positons au fluorodéoxyglucose 18 dans la détection des neurofibrosarcomes au cours de la neurofibromatose de type 1. B Bensaid et al . Ann Dermatol Venereol 2007;134:735-41
Positron Emission Tomography of Schwannomas: Emphasizing Its Potential in Preoperative Planning. S Beaulieu et al . AJR: 2004;182:971
Quantitative F18-Fluorodeoxyglucose Positron Emission Tomography Accurately
Characterizes Peripheral Nerve Sheath Tumors as Malignant or Benign. M R. Benz. Cancer 2010;116:451–8.
Prognostic relevance of FDG PET in patients with neurofibromatosis type-1 and malignant peripheral nerve sheath tumours .W Brenner. Eur J Nucl Med Mol Imaging 2006; 33:428–432
[18F]FDG PET/CT in the diagnosis of malignant peripheral nerve sheath tumours in neurofibromatosis type-1. VS Warbey et al. Eur J Nucl Med Mol Imaging 2009; 36:751–757
Utility of positron emission tomography for tumour surveillance in children with neurofibromatosis type 1 M Moharir. Eur J Nucl Med Mol Imaging 2010; 37:1309–1317
Evaluation of intratumoural heterogeneity on 18F-FDG PET/CT for characterization of peripheral nerve sheath tumours in neurofibromatosis type 1, J Salamon
Eur J Nucl Med Mol Imaging DOI 10.1007/s00259-012-2314-6;2012
Potential Role of 18 FluoroDeoxyglucose - Positron Emission Tomography/Computed tomography in differentiating benign neurofibroma from malignant . K Karabatsou. Neurosurgery 2009; 65:A160–A170
18-Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) Evaluation of
Nodular Lesions in Patients With Neurofibromatosis Type 1 and Plexiform
Neurofibromas (PN) or Malignant Peripheral Nerve Sheath Tumors (MPNST). H Meany. Pediatr Blood Cancer 2013;60:59–64
18-Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) Evaluation of
Nodular Lesions in Patients With Neurofibromatosis Type 1 and Plexiform
Neurofibromas (PN) or Malignant Peripheral Nerve Sheath Tumors (MPNST). HMeany et al. Pediatr Blood Cancer 2013;60:59–64
Can we differentiate malignant peripheral nerve sheath tumor from benign neurofibroma without invasive sampling. FS Simsek et al. World J Nucl Med 2019;18:66-68.
The Role of [18F]FDG-PET/CT in Predicting Malignant Transformation of Plexiform
Neurofibromas in Neurofibromatosis-1. D Tovmassian et al. Intern J Surg Oncol 2016; http://dx.doi.org/10.1155/2016/6162182The value of 18F-FDG PET/CT in patient with neurofibromatosis type 1.A case report and literature review. J Ren et al. Medicine 2018;97:20The characteristics of 76 atypical neurofibromas as precursors to neurofibromatosis 1 associated malignant peripheral nerve sheath tumors. CS Higham et al. NeuroOncol 2018;20:818-825Monitoring of plexiform neurofibroma in children and adolescents with Neurofibromatosis type 1 by [18F]FDG-PET imaging. Is it of value in asymptomatic patients? AA Azizi et al. Ped Blood Cancer 2018;65: e26733