Primary Intraosseous Malignant Peripheral Nerve Sheath Tumor of the Medial Cuneiform: A Case Report and Review of the Literature.

Peripheral nerve sheath tumors (benign and malignant) usually arise in the soft tissues and are unusual in bone. Intraosseous peripheral nerve sheath tumors are usually benign and constitute approximately 0.2% of all bone tumors. Intraosseous malignant peripheral nerve sheath tumors (MPNSTs) are uncommon and usually result from secondary invasion. Only a few cases of primary intraosseous MPNSTs have been reported in published studies, and these were localized mostly in the mandible (approximately 50%) or maxilla, spine, and, occasionally, in the appendicular skeleton. To the best of our knowledge, we report the first case of primary intraosseous MPNST involving a midtarsal bone (medial cuneiform). The patient was a 62-year-old female who presented with pain and tenderness but without swelling. Imaging revealed nonspecific findings, and the preoperative computed tomography-guided biopsy findings were consistent with MPNST. The patient was treated with neoadjuvant radiotherapy, followed by wide local excision and allograft reconstruction. At the final follow-up examination (24 months), the graft had been incorporated without evidence of local recurrence or distant disease. The patient with primary intraosseous MPNST of the medial cuneiform described in the present report presented with nonspecific clinical and radiologic findings. Thus, a high index of suspicion and histopathologic examination, including immunohistochemistry, are necessary for an accurate diagnosis.