Imaging diagnosis of plexiform neurofibroma- unravelling the confounding features: A report of two cases

Peripheral nerve sheath tumors such as neurofibroma, comprise 5% of all benign soft tissue tumors and usually occur due to an underlying neurofibromatosis. A plexiform neurofibroma, which is a tumor occurring exclusively in neurofibromatosis1, is a rare entity and is an uncommon variant of neurofibroma. We report the clinical and imaging features of plexiform neurofibroma in two young male patients, in whom the imaging diagnosis was confirmed after biopsy. The report not only aims to highlight the characteristic imaging features of plexiform neurofibroma but we also emphasize the ultrasound appearances which are significantly characteristic and can effectively lead to the correct diagnosis at the preliminary stage of investigation. The tumors which originate from nerve sheath, are large, lobulated masses and demonstrate typical imaging features of simultaneous involvement of subcutaneous and cutaneous tissues along with infiltrative invasion of deeper structures. The tumors characteristically display fat and fluid contents and a “target sign’ on evaluation by ultrasound, CT and MRI. Imaging plays an important role in confirming the diagnosis, delineating involved structures, excluding simulating conditions and forewarning a possible malignant transformation.