Multicentric malignant peripheral nerve sheath tumor

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We present a case of malignant peripheral nerve sheath tumor of multicentric origin, an extremely rare condition. A 25-year-old man was admitted to hospital ...

Clinical Imaging 31 (2007) 363 – 366

Multicentric malignant peripheral nerve sheath tumor Ersin Ozturka,4, Iclal Erdemb, Guner Sonmeza, Aptullah Haholuc, Huseyin Onur Sildiroglua, Hakan Mutlua, C. Cinar Basekima, Esref Kizilkayaa a

Department of Radiology, GATA Haydarpasa Teaching Hospital, Istanbul, Turkey b Department of Radiology, Siirt Government Hospital, Siirt, Turkey c Department of Pathology, GATA Haydarpasa Teaching Hospital, Istanbul, Turkey Received 15 December 2006; received in revised form 17 April 2007; accepted 21 April 2007

Abstract We present a case of malignant peripheral nerve sheath tumor of multicentric origin, an extremely rare condition. A 25-year-old man was admitted to hospital with presenting symptoms of cough, dyspnea and left lateral back pain. Computed tomography and magnetic resonance imaging revealed extrapleural masses in the left hemithorax in addition to synchronous left inguinal mass. After surgical resection of the masses from the thoracic and inguinal regions, histological examination confirmed the preoperative diagnosis of malignant peripheral nerve sheath tumor. D 2007 Elsevier Inc. All rights reserved. Keywords: Malignant peripheral nerve sheath tumor; Multicentric origin; Computed tomography; Magnetic resonance imaging

1. Introduction Malignant peripheral nerve sheath tumor (MPNST) is a rare condition that may arise from any peripheral nerves [1]. More than 90% of these tumors are benign and overall 10% are malignant [2]. Among all these tumors only 10% are multiple. Magnetic resonance (MR) imaging is the imaging modality of choice. Radiologically, most MPNSTs have typical fusiform shape oriented longitudinally in the nerve distribution. They may be lobulated in rare cases. We present a case of MPNST of multicentric origin, which is an extremely rare condition. 2. Case report A 25-year-old man was admitted to hospital with presenting symptoms of coughing, dyspnea and left lateral back pain. He was a nonsmoker and his family history was

Abbreviations: MPNST, malignant peripheral nerve sheath tumor; NF, neurofibromatosis; MR, magnetic resonance; CT, computed tomography. 4 Corresponding author. GATA Haydarpasa Egitim Hastanesi Radyoloji Servisi, Uskudar, Istanbul, Turkey. Tel.: +90 212 2797578 (home), +90 212 5422879 (work); fax: +90 212 5422808. E-mail address: [email protected] (E. Ozturk). 0899-7071/07/$ – see front matter D 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.clinimag.2007.04.028

unremarkable. At physical examination, blood pressure, pulse and temperature were normal. He had a firm mass in the left inguinal region. Laboratory findings were within normal limits. In the left inguinal region, laterally to the femoral vascular structures, there was an oval, homogeneous, hypoechoic, 5935-mm lesion at superficial ultrasound, which suggested lymphadenopathy. The chest radiograph showed extra-parenchymal opacities in the left hemithorax. Computed tomography (CT) of the chest revealed extraparenchymal round masses with lobular contours in the left hemithorax (Fig. 1A). The attenuation of the masses was 50–60 HU. The left inguinal mass was seen hypodense to muscle in CT images obtained at the level of the symphysis pubis (Fig. 1B). This left inguinal mass was considered as a reactive lymph node enlargement or a metastastic lymph node. Thoracic MR imaging showed lobulated extra-parenchymal masses that were hypointense on the T1-weighted images and of intermediate intensity on T2-weighed images (Fig. 2A–C). The lesions did not extend into the neural foramen. A fine-needle aspiration biopsy was performed on one of the left extra-parenchymal lesion, and the sample taken revealed malignant cells. A Tru-cut biopsy showed poorly differentiated malignant tumor having mostly pleomorphic

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Fig. 1. (A) Thorax CT scan (mediastinal window) shows extra-parenchymal mass (black arrows) in the left hemithorax. (B) CT scan obtained at the level of the symphysis pubis shows left inguinal mass (white arrow).

spindle cells forming bundles and lobules. Meanwhile, CT of the neck was performed. Except for a few nonspecific reactive hyperplastic cervical lymph nodes, no abnormality was observed. A bronchoalveolar lavage was performed and no malignant cells were observed. In addition, the fiberoptic bronchoscopy revealed no abnormality. Whole-body scintigraphy was also normal. Subsequently, an 18F-FDG-PET scan was performed and increased uptake was seen. Imaging findings were consistent with a malignant process in extraparenchymal area contiguous with the apical posterior segment of the left upper lobe, the lateral basal segment of the left inferior lobe and the lateral part of the medial zone. A Tru-cut biopsy from another extra-parenchymal lesion revealed MPNST. Resection of a lymph node from the left inguinal region yielded reactive hyperplasia. A Trucut biopsy from the left inguinal lesion showed a sarcomatous malignant tumor morphologically similar to the samples from the extrapleural masses previously taken. After surgical resection of the masses from the thoracic and inguinal region, histological examination confirmed the preoperative diagnosis of MPNST. Bilaterally, lung parenchyma metastases were detected by CT after 1 year of follow-up.

3. Discussion MPNSTs are malignant variants of peripheral nerve sheath tumors that are derived from a peripheral nerve. They are rare tumors that arise from embryonic neural crest cells and are associated with neurofibromatosis (NF) and with previous irradiation [3]. Plexiform neurofibromas can give rise to malignant peripheral nerve sheath tumors [4,5]. The studies suggest that there is a significant relationship between internal plexiform neurofibromas and MPNSTs, and patients with NF Type 1 with these benign tumors have higher risk for malignancy [6]. These tumors are situated closed to a nerve trunk and they occur in the deep soft tissues [7]. MPNSTs were previously referred to as malignant schwannoma, neurogenic sarcoma and neurofibrosarcoma. Currently, these highly aggressive tumors are termed as malignant peripheral nerve cell tumors by the World Health Organization [7]. Malignant peripheral nerve cell tumors are generally solitary and clinically occult [3]. However, they can also be aggressive, locally invasive and cause erosion of the ribs and vertebral bodies and neural foraminal enlargement [2]. Typically, malignant degeneration of benign neurogenic

Fig. 2. Coronal T1-weighted (A), T2-weighted (B) and contrast-enhanced T1-weighted (C) MR images show lobulated masses in the left hemithorax.

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tumors manifests as pain. Half of MPNSTs are associated with NF and 10% with previous irradiation [1]. Our patient had nonspecific clinical symptoms such as cough and dyspnea, but no history of irradiation or NF. Radiologically, MPNSTs and neurofibromas may appear indistinguishable [7]. A review of the literature shows that, on plain radiographs, lesions usually appear as a smooth rounded or oval mass, which may be lobulated in rare cases. Erosive adjacent bony changes and enlargement of the neural foramen may also be observed [2]. On CT scan, most lesions appear as a homogeneously low or isoattenuated, well-demarcated oval or round mass in precontrast scans [8]. In postcontrast images, CT attenuation values are variable [9]. MR imaging may be helpful in detecting the location and extent of intrathoracic tumors by using multiplanar capacity and high-contrast resolution. Lesions have low to intermediate signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images [10]. According to a study performed by Van Herendael et al. [11], some MRI findings suggestive of MPNST were location on the course of a large nerve, nodular morphology, and overall nonhomogeneity on T1-weighted images, T2-weighted images and contrastenhanced T1-weighted images. Also, there are studies that by the help of some specific appearances MR imaging may be useful in differentiation of benign and malignant peripheral nerve sheath tumors. Bhargava et al. [12] emphasized the use of the target sign in MR imaging to make a differentiation between benign neurofibromas and their malignant counterparts. They noticed that T2-weighted MR imaging of soft tissue tumors of neural origin might show round lesions with a central hypointensity and a hyperintense rim resembling a target. They defined the btarget signQ as a mass consisting of a solitary target, or a multicompartmental mass in which the largest component consists of multiple targets. Their study revealed that the target sign was seen in all benign neurofibromas and only a few malignant peripheral nerve sheath tumors showed the target sign on MRI. So they concluded that the target sign on T2-weighted MR imaging was helpful in differentiating neurofibromas from malignant peripheral nerve sheath tumors. F18-deoxyglucose positron emission tomography (FDG-PET) is another way for evaluating biological tumour. In a study about differentiation of benign neurofibromas and malignant peripheral nerve sheath tumours, Cardona et al. [13] claimed that benign lesions did not demonstrate high FDG uptake, whereas the standard uptake value was significantly higher in MPNST. They concluded that FDG-PET allows discrimination of benign from malignant neurogenic tumours. This should be particularly useful in patients with NF as FDG-PET may help to avoid multiple surgical procedures for benign tumours [13]. Chest X-rays revealed well-defined, small, round opacities in our patient’s left hemithorax. CT of the thorax revealed round, extraparenchymal, intermediately attenuated lesions with lobulated, well-defined contours. At lung MR imaging, there

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were lobulated, extra-parenchymal masses that were hypointense on T1-weighted images and intermediately intense on T2-weighted images, with lobulated contours. There was no target sign. The lesions were determined to be malignant in an 18F-FDG-PET scan as the standard uptake value was significantly high. The histopathologic analysis revealed MPNST. It is important to note that there was also a left inguinal mass. After performing several tests, we determined that the mass was a second, coincidental MPNST. A review of the literature revealed only a few cases of coexistent MPNST [14]. The treatment of choice in MPNST is surgical resection. Neoadjuvant chemotherapy is rarely administered since distinguishing between benign and malignant neoplasms is difficult unless histopathologic evaluation is performed. In addition, no chemotherapy is known to be completely effective [3]. Prognosis is poor in MPNST. Reported 5-year survival rates were 34–52% in two studies [15,16]. There are several factors that affect survival, such as location, size, grade and the presence of metastasis and NF [3]. In conclusion, MPNST of multicentric origin is an extremely rare neoplasm that is difficult to diagnose. Many radiological methods are available, although MRI seems to be more effective in the overall assessment. Although extremely rare, the possibility of MPNST of multicentric origin should be kept in mind in assessing soft tissue tumors in the different sides of body. Also because of known relationship of MPNSTs with NF-1, performing genetic counseling of family members suspected to have NF-1 may be useful.

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