Primary Intraosseous Malignant Peripheral Nerve Sheath Tumor of the Humerus: Report of a Rare Case.

Malignant peripheral nerve sheath tumors (MPNSTs) usually arise in the soft tissues. Intraosseous MPNSTs are rare. They may arise de novo but are typically associated with neurofibromatosis type 1 (NF1) and radiation therapy. Our patient is a 58-year-old female patient that presented with right shoulder pain. An MRI showed a shoulder mass, and percutaneous bone biopsy demonstrated morphology suggestive of an MPNST; besides, on immunohistochemistry, SOX10 was positive, and H3K27me3 expression was entirely lost. The patient underwent total resection of the right proximal humerus and endoprosthetic shoulder reconstruction, followed by radiation therapy and chemotherapy. Only a few cases in the mandible, spine, maxilla, ulna, metacarpal, tarsal, and one in the humerus have been published. In this paper, we contribute with an additional case of primary intraosseous MPNST in the humerus and a brief literature review.