Sporadic Malignant Perineurioma: A Rare Diagnosis Among Malignant Peripheral Nerve Sheath Tumors

Background: Malignant perineurioma is a rare subset of malignant peripheral nerve sheath tumors (MPNSTs) with ultrastructural and immunohistochemical features of perineurial differentiation, distinguishing it from other MPNSTs, which typically demonstrate Schwannian features. The clinical course and prognosis of this rare tumor is not well defined. Methods: The electronic medical records were searched for patients with a diagnosis of MPNST. Patients with a pathologic diagnosis of malignant perineurioma or MPNST with perineurial features were identified and further evaluated. Results: Five patients with malignant perineurioma, or MPNST with perineurial features, were identified. Four patients (2 male and 2 female) were included with tumors associated with a common digital nerve, small muscular branch to the deltoid, sciatic nerve, and accessory nerve. One patient with the pathology diagnosis meeting inclusion criteria was excluded, as no clinical information was available for this patient. Conclusions: Patients in our series presented at varied stages of disease. Clinical courses after diagnosis of malignant perineurioma, where follow-up was available, were largely uncomplicated with regard to recurrence and metastatic disease. Careful follow-up is indicated, and further work is needed to characterize the clinical course of these rare tumors.