Plurifocal malignant peripheral nerve sheath tumor ... - Springer Link

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Abstract Malignant peripheral nerve sheath tumors. (MPNSTs) are sarcomas that derive from peripheral nerves or from cells associated with the nerve sheath.

Jpn J Radiol (2009) 27:320–323 DOI 10.1007/s11604-009-0343-2

CASE REPORT

Plurifocal malignant peripheral nerve sheath tumor demonstrated by 18F-fluorodeoxyglucose positron emission tomography/computed tomography Francesco Bertagna · Giovanni Bosio · Giorgio Biasiotto Giordano Savelli · Carlo Rodella · Raffaele Giubbini Josh Rosenbaum · Abass Alavi

Received: May 18, 2009 / Accepted: June 14, 2009 © Japan Radiological Society 2009

Abstract Malignant peripheral nerve sheath tumors (MPNSTs) are sarcomas that derive from peripheral nerves or from cells associated with the nerve sheath. Magnetic resonance imaging is the main diagnostic imaging modality for evaluating MPNSTs. Computed tomography (CT) of the chest is the main imaging modality used to screen for distant disease, and bone scanning is considered useful for identifying selected metastases. Fluorodeoxyglucose positron emission tomography (FDG-PET) has been useful for differentiating malignant nerve sheath tumors from benign lesions and appears to be able to forecast prognosis. We report a case of a patient with neurofibromatosis 1 (NF1) with a histological diagnosis of MPNST, which was diagnosed by biopsy of a posterior right thigh mass examined by 18F-FDG-PET/CT.

Key words PET · Malignant peripheral nerve sheath tumor (MPNSTs) · Neurofibromatosis

Introduction

F. Bertagna (*) · G. Bosio · G. Savelli Department of Nuclear Medicine, Spedali Civili di Brescia, Piazza Spedali Civili, 1, 25123 Brescia, Italy Tel. +39-30-3995468; Fax +39-30-3995420 e-mail: [email protected]

Malignant peripheral nerve sheath tumors (MPNSTs) are sarcomas that derive from peripheral nerves or from cells associated with the nerve sheath (Schwann cells, perineural cells, fibroblasts). They may develop in patients affected by neurofibromatosis 1 (NF1). Neurofibromas are the most common tumor associated with NF1, and the plexiform neurofibroma subtype represents a major cause of morbidity.1 MPNSTs usually arise from preexisting benign plexiform neurofibromas and metastasize widely. Differentiating between benign and malignant tumours is extremely important as MPNSTs frequently have a poor prognosis but can be difficult to find in the presence of multiple benign tumors. The clinical manifestations of malignancy include pain not otherwise explained, rapid increase in the size of the lesion, change in consistency, and neurological deficit.2,3

G. Biasiotto Dipartimento Materno Infantile e Tecnologie Biomediche, University of Brescia, Brescia, Italy

Case report

C. Rodella Health Physics Unit, Spedali Civili Brescia, Brescia, Italy R. Giubbini Department of Nuclear Medicine, University of Brescia, Brescia, Italy J. Rosenbaum · A. Alavi Division of Nuclear Medicine, University of Pennsylvania Medical Center, Philadelphia, PA, USA

We report the case of a patient with NF1 with a histological diagnosis of MPNST diagnosed by biopsy of a posterior right thigh mass. The patient underwent fluorodeoxyglucose-positron emission tomography/ computed tomography (18F-FDG-PET/CT) for staging purposes following magnetic resonance imaging (MRI), CT, and ultrasonography (US). 18F-FDG-PET/CT was performed in the fasting state (at least 6 h); the glucose

Jpn J Radiol (2009) 27:320–323

Fig. 1. Coronal positron emission tomography (PET) images show high uptake at the posterior right thigh mass

Fig. 2. Coronal PET images showing high uptake at the popliteal mass

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Jpn J Radiol (2009) 27:320–323

Fig. 3. Axial computed tomography (CT), PET, and fusion images of the pectoral lesion

level was 82 mg/dl. A FDG dose of 424 MBq was administered intravenously and a two-dimensional (2D) mode ordered subset–expectation maximization (OS-EM) imaging (with septa) was acquired 60 min after injection on a Discovery ST PET/CT tomograph (General Electric, Milwaukee, WI, USA) with standard CT parameters (80 mA, 120 KV without contrast; 4 min per bed–PET–step of 15 cm). The reconstruction was performed in a 128 × 128 matrix and 60 cm field of view. The PET images were analyzed visually and semiquantitatively by measuring the standardized uptake value (SUV). The study revealed intense maximum uptake at the mass located in the right thigh (SUVmax 4.8) (Fig. 1), left popliteal region (SUVmax 3.7) (Fig. 2), and right major pectoral muscle (Fig. 3). Light uptake (SUVmax 1.5–3.0) was present at some of the solid masses described

on CT at the left supraclavicular region and paratracheal and paraesophageal regions near the ninth thoracic vertebra. No uptake was seen at other solid masses in the right iliac fossa or right gluteus probably because of their benign nature.

Discussion MPNSTs are aggressive tumors, and the patients’ prognosis is generally poor. Accurate staging to identify widespread disease and discriminate benign lesions from malignant ones, which significantly affects the prognosis, is essential. Magnetic resonance imaging is the main diagnostic imaging modality as it allows precise evaluation of the planes invaded, the tumor’s heterogeneity, its margins,

Jpn J Radiol (2009) 27:320–323

and the presence of edema surrounding the lesion. MPNSTs are commonly found in the extremities (46%– 61%) and the trunk (15%–46%). The large and medium nerves are more frequently affected by these lesions.4,5 MPNSTs usually metastasize to the lungs, bone, and pleura with a local recurrence rate of 40%-65% and a distant recurrence rate of 40%-68%. Computed tomography of the chest is the main imaging tool to screen for distant disease, and bone scanning is useful for identifying metastatic bone disease. 18 F-FDG-PET/CT imaging has been widely used in oncology, but its value for assessing MPNSTs—even though it has been demonstrated to be useful in published papers—is not extensively studied in the literature.6–8 18F-FDG-PET/CT is extremely helpful for differentiating malignant nerve sheath tumors from benign lesions and therefore may provide prognostic information in this setting.2,9 In particular, Ferner et al. studied 105 patients with NF1 tumors, including 29 cases of MPNST, showing high diagnostic accuracy (sensitivity 89%, specificity 95%).9 Even in our single case, the results confirmed the high accuracy of 18FFDG-PET/CT and its diagnostic value in a patient with multiple lesions. Most plexiform neurofibroma subtype (PN) lesions are benign and have low FDG–PET SUV values. FDGPET/CT imaging predicts PN tumor growth in patients with NF1; it may help in decision making1 and is a highly sensitive and specific imaging modality for the diagnosis of MPNST in NF1 patients. Some authors recommend performing early (90 min) and delayed (4 h) imaging for accurate lesion characterization, using a cutoff SUVmax of 3.5 to achieve the best compromise between sensitivity and specificity in the diagnosis of MPNSTs.3 In our study, we had a reliable metabolic lesion evaluation 60 min after the injection with a less time-consuming procedure and better patient throughput. The treatment of choice is surgical resection, when feasible, to achieve complete excision of the tumor. Radiation therapy (before and after surgery) is also an important therapeutic modality in the management of these patients. Chemotherapy is usually used for systemic and metastatic disease and is employed only for high-grade disease.10

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Conclusion In this clinical case, 18F-FDG-PET/CT helped with the discrimination between benign lesions related to the known NF1 from the malignant transformed ones. It also assisted clinician decision making.

References 1. Fisher MJ, Basu S, Dombi E, Yu JQ, Widemann BC, Pollock AN, et al. The role of [18F]-fluorodeoxyglucose positron emission tomography in predicting plexiform neurofibroma progression. J Neurooncol 2008;87:165–71. 2. Ferner RE, Gutmann DH. International consensus statement on malignant peripheral nerve sheath tumors in neurofibromatosis 1. Cancer Res 2002;62:1573–7. 3. Warbey VS, Ferner RE, Dunn JT, Calonje E, O’Doherty MJ. [18F]FDG PET/CT in the diagnosis of malignant peripheral nerve sheath tumours in neurofibromatosis type-1. Eur J Nucl Med Mol Imaging 2009;36:751–7. 4. Ducatman BS, Scheithauer BW, Piepgras DG, Reiman HM, Ilstrup DM. Malignant peripheral nerve sheath tumours: a clinicopathologic study of 120 cases. Cancer 1986;57: 2006–21. 5. Woodruff JM. Pathology of tumors of the peripheral nerve sheath in type 1 neurofibromatosis. Am J Med Genet 1999;89: 23–30. 6. Ferner RE, Lucas JD, O’Doherty MJ, Hughes RA, Smith MA, Cronin BF, et al. Evaluation of (18)fluorodeoxyglucose positron emission tomography [(18)FDG PET] in the detection of malignant peripheral nerve sheath tumors arising from within plexiform neurofibromas in neurofibromatosis 1. J Neurol Neurosurg Psychiatry 2000;68:353–7. 7. Hsu CH, Lee CM, Wang FC, Fang CL. Neurofibroma with increased uptake of [F-18]-fluoro-2-D-glucose interpreted as a metastatic lesion. Ann Nucl Med 2003;17:609–11. 8. Otsuka H, Graham MM, Kubo A, Nishitani H. FDG-PET/ CT findings of sarcomatous transformation in neurofibromatosis: a case report. Ann Nucl Med 2005;19:55–8. 9. Ferner RE, Golding JF, Smith M, Calonje E, Jan W, Sanjayanathan V, et al. [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. Ann Oncol 2008;19:390–4. 10. Johansson G, Mahller YY, Collins MH, Kim MO, Nobukuni T, Perentesis J, et al. Effective in vivo targeting of the mammalian target of rapamycin pathway in malignant peripheral nerve sheath tumors. Mol Cancer Ther 2008;7: 1237–45.

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