Rare case of Malign Peripheral Nerve Sheath Tumor complicating a solitary giant neurofibroma of the thigh

INTRODUCTION AND IMPORTANCE: Malign Peripheral Nerve Sheath Tumor is rare and can occur on a solitary neurofibroma or as part of neurofibromatosis type 1. The occurrence of a giant solitary neurofibroma in the thigh is rare and its complication in MPNST is much rarer. The diagnosis is based on a combination of radiological, histological and immunohistochemical evidence. CASE PRESENTATION: We present the case of a 55 years old woman who presented a mass of the posterior aspect of the thigh without any other abnormality on systemic examination. MRI showed a T1 hyposignal and a T2 hypersignal and the biopsy performed was in favor of a neurofibroma. After surgical resection, the histological study of the surgical specimen revealed an MPNST developing on a pre-existing neurofibroma. After 5 months, the patient had moderate knee stiffness with thigh amyotrophy. CLINICAL DISCUSSION: The occurrence of MPNST on a giant solitary neurofibroma of the thigh is extremely rare. MRI allows evoking the diagnosis but radiologists are confronted with a problem of differential diagnosis. Histological examination supports the diagnosis in addition to immunohistochemical examination. Only surgical treatment can give hope for a cure. Recurrences remain frequent with a 5-year survival of 50 %. CONCLUSION: Early diagnosis is essential to prevent the evolution of the tumor and the occurrence of poor prognostic factors compromising the management, increasing the risk of recurrence and affecting the overall survival of patients.