Intraosseous epithelioid malignant peripheral nerve sheath tumor of the phalanx. Case report

The rare primary bone sarcomas: imaging-pathological correlation

Rare primary bone sarcomas are challenging entities both radiologically and pathologically. These include the diagnoses of spindle cell sarcoma (leiomyosarcoma, fibrosarcoma, synovial sarcoma, and malignant peripheral nerve sheath tumor), pleomorphic liposarcoma, and undifferentiated pleomorphic sarcoma. The radiographic and cross-sectional imaging features of each of these tumors are presented, along with current key pathological concepts. Frequently non-specific, the radiological appearances must be correlated with all clinical and pathological information available to enable an accurate diagnosis.

Intraosseous malignant peripheral nerve sheath tumor of the sacrum in a patient with neurofibromatosis type I

Malignant intraosseous peripheral nerve sheath tumor is a very rare malignancy most commonly seen in patients with neurofibromatosis type 1. This tumor almost exclusively occurs in the maxillofacial region, with manifestation of this tumor in other regions of the skeleton infrequently reported. We describe a 23-year-old female with previously undiagnosed neurofibromatosis type 1 presenting with lower extremity weakness, paresthesias, and bowel/bladder symptoms. The patient had an aneurysmal lytic bone lesion centered in the upper sacrum with invasion of the L5 vertebral body. On MRI, the lesion was homogeneously isointense to muscle on T1, heterogeneously hyperintense to muscle on T2, and demonstrated homogeneously avid contrast enhancement. Multiple additional small lesions with similar imaging characteristics were identified in the paraspinal soft tissues. Low grade malignant peripheral nerve sheath tumor of the sacrum was diagnosed on biopsy. The patient was treated with sacral resection and radiation therapy for local disease control.

Malignant Peripheral Nerve Sheath Tumor of the Femur: A Rare Diagnosis Supported by Complete Immunohistochemical Loss of H3K27me3

The histological diagnosis of malignant peripheral nerve sheath tumor (MPNST) is challenging because of the wide morphological spectrum and suboptimal performance of conventional immunohistochemical markers. MPNST arising primarily in the bone is exceptional, and its definitive diagnosis, particularly out of the neurofibromatosis type 1 (NF1) context, is even more problematic. Recurrent inactivation of EED or SUZ12 in a majority of MPNSTs results in a complete loss of trimethylated histone H3 at lysine 27 (H3K27me3) immunoreactivity, making it a highly specific biomarker of MPNSTs. In this article, we report a case of sporadic MPNST of the proximal femur that showed complete loss of H3K27me3. The patient was treated with limb-sparing surgery and postoperative radiotherapy. He developed multiple lung and bone metastases 4 months after surgery. Our case confirms the utility of H3K27me3 immunohistochemistry to yield a definitive diagnosis of sporadic MPNST in a rare primary site.

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.

Epithelioid malignant peripheral nerve sheath tumor. Report of a case with inflammatory infiltration

The epithelioid malignant peripheral nerve sheath tumor (EMPNST) is a rare sarcoma originating from the supportive non-neuronal components of peripheral nerves. Our patient was a 75-year-old Japanese man who presented with complaints about pain and a mass in the left thigh. Characteristic histopathological features were large epithelioid-like cells closely resembling a malignant melanoma or another type of soft tissue tumor. Notable infiltration of neutrophils in the tumor was seen. Immunohistochemically, the tumor cells proved positive for S-100, NSE, GFAP, MBP, chromogranin A and synaptophysin, and negative for CEA, keratin, HMB-45, G-CSF, and GM-CSF. Tumor-related inflammatory infiltration may be caused by an autonomous production of some cytokines. However, these tumor cells were negative for G-CSF and GM-CSF so that the mechanism triggering inflammatory infiltration is unclear. Electron microscopy revealed the presence of an extracellular basal lamina, intermediate cell junctions, and numerous dense-cored granules in the cytoplasm. These findings suggested a schwannian derivation, consistent with the diagnosis of EMPNST. There have been reports on S-100 positivity and HMB-45 negativity of this tumor type, but to the best of our knowledge, this is the first description of an EMPNST positive for MBP, chromogranin A, and synaptophisin. Where unequivocal features are lacking, these markers might be useful for differential diagnosis.