Perineurial Malignant Peripheral Nerve Sheath Tumor of the Cauda Equina: Diagnostic Challenge

TL;DR

A rare case of perineurial MPNST in the cauda equina is presented, highlighting the diagnostic challenges and the importance of early treatment.

Contribution

This case report adds to the limited literature on perineurial MPNSTs and emphasizes the need for early diagnosis.

Findings

The tumor was initially misdiagnosed due to lack of distinctive imaging features.

A definitive diagnosis was made after open biopsy two years later.

Perineurial MPNSTs may have a better prognosis compared to other MPNST subtypes.

Abstract

Malignant peripheral nerve sheath tumors (MPNSTs) are rare sarcomas with an extremely rare perineurial subtype. Herein, we present a case of a perineurial MPNST in the cauda equina. Clinically and radiologically, a mass extending from within the spinal canal at the L5 level to outside the intervertebral foramen was identified, raising suspicion of a neurogenic tumor as the primary diagnosis. Computed tomography-guided biopsy suggested an intermediate- to low-grade malignancy; however, a definitive diagnosis could not be established. Two years later, worsening neurological symptoms prompted further imaging, which revealed significant tumor growth and bone invasion. Open biopsy was performed to obtain a definitive diagnosis of perineurial MPNST. MPNSTs lack distinctive imaging features and are generally diagnosed based on a combination of radiological and histopathological findings. Although MPNSTs have a poor prognosis, the perineurial subtype is considered to have a relatively favorable outcome. Given these factors, early diagnosis followed by surgical resection or radiation therapy is recommended.

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