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Malignant Peripheral Nerve Sheath Tumor Is a Challenging Diagnosis: A Systematic Pathology Review, Immunohistochemistry, and Molecular Analysis in 160 Patients From the French Sarcoma Group Database

Le Guellec, Sophie MD; Decouvelaere, Anne-Valérie MD, PhD; Filleron, Thomas PhD; Valo, Isabelle MD; Charon-Barra, Céline MD; Robin, Yves-Marie MD; Terrier, Philippe MD; Chevreau, Christine MD; Coindre, Jean-Michel MD

The American Journal of Surgical Pathology: July 2016 - Volume 40 - Issue 7 - p 896–908
doi: 10.1097/PAS.0000000000000655
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An accurate histopathologic diagnosis is essential for an adequate treatment of soft tissue sarcomas. The diagnosis of malignant peripheral nerve sheath tumor (MPNST) can be complex, particularly outside the neurofibromatosis type 1 (NF1) context. MPNST is a rare malignancy, and due to the lack of specific histologic criteria, several differential diagnoses must be considered. A total of 350 patients diagnosed with MPNST (from 1990 to 2013) were retrieved from the French sarcoma network (RRePS) and the Conticabase (Connective Tissue Cancer Network database). Tumor samples were available for 160 cases (45.2%). Pathology review, immunohistochemistry (IHC), and molecular analysis (when dealing with a monomorphic sarcoma) were systematically performed. Patient, tumor, and treatment characteristics were evaluated to identify prognostic factors for the definitive primary MPNST (n=106) cohort. Twenty-nine tumors (18.1%) initially diagnosed as MPNST were reclassified on the basis of histologic review, IHC, and molecular analysis. Patients with NF1 disease comprised 64% of the remaining cohort. The 5-year overall survival for patients from the entire cohort was 47%, 34.8% for NF1 patients, and 68.5% for patients without NF1 disease, making NF1 syndrome an independent poor prognostic factor of survival. Positive margins and lack of radiation therapy were independent predictors of local recurrence. The Fédération Nationale des Centres de Lutte Contre le Cancer tumor grade was an independent prognostic indicator of metastasis. Given the therapeutic implications of a misdiagnosis, the systematic pathology review, IHC, and molecular analysis (when dealing with monomorphic sarcoma) strategy allowed reclassification of 20% of cases, mainly the sporadic MPNSTs.

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Departments of *Pathology

Biostatistics

**Oncology, Institut Claudius Regaud, IUCT-Oncopole, Toulouse

Department of Pathology, Centre Léon Bérard, Lyon

§Department of Pathology, Centre Paul Papin, Angers

Department of Pathology, Centre Georges-Francois Leclerc, Dijon

Department of Pathology, Centre Oscar Lambret, Lille

#Department of Pathology, Institut Gustave Roussy, Villejuif

††Department of Pathology and INSERM U916, Institut Bergonié

‡‡University Bordeaux Ségalen, Bordeaux, France

The data used in this publication were provided by the Conticanet (Connective Tissue Cancer Network) database (https://conticabase.sarcomabcb.org) and the French sarcoma network RRePS (https://rreps.sarcomabcb.org). These databases are financially supported by Conticanet and INCa (Institut National du Cancer).

The following centers participated in the study: Paul Papin Center, Angers; Institut Bergonié, Bordeaux; Jean Perrin Center, Clermont-Ferrand; Georges-Francois Leclerc Center, Dijon; Oscar Lambret Center, Lille; Léon-Bérard Center, Lyon; Antoine Lacassagne Center, Nice; Institut Gustave Roussy, Paris, France; CHU Toulouse, Toulouse; Institut Claudius Regaud, Toulouse, and CHU Bretonneau, Tours.

The results of this study were presented in part at the United States and Canadian Academy of Pathology Meeting, Seattle, WA, March 12-18, 2016.

Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.

Correspondence: Sophie Le Guellec, MD, Department of Pathology, Institut Claudius Regaud, IUCT- Oncopole., 1 avenue Irène Joliot-Curie, 31059 Toulouse Cedex 9, France (e-mail: LeGuellec.sophie@iuct-oncopole.fr).

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