Intradural extramedullary spinal nerve sheath myxoma: a report of two cases

Spinal myxomas: review of a rare entity

Intramuscular myxomas are rare, benign mesenchymal tumours, occurring predominantly in large skeletal muscles as large, slow-growing and painless masses. Spinal occurrence is rare, and may present incidentally, or diagnosed via localized symptoms secondary to local infiltration of surrounding structures. Differential diagnosis based on imaging includes sarcomas, meningiomas and lipomas. We discuss two contrasting cases presenting with well-circumscribed cystic paraspinal lesions indicative of an infiltrative tumour and discuss the radiological and histological differences that distinguish myxomas from similar tumours. Surgical resection of the tumour was performed in both cases, however one patient required surgical fixation due to bony erosion secondary to tumour infiltration. Immuno-histopathological analysis confirmed the diagnosis of a cellular myxoma. Follow up imaging at 6 months confirmed no symptomatic or tumour recurrence in both cases. Histological analysis is the definitive means for diagnosis to differentiate myxomas from other tumours. Recurrence is rare if full resection is achieved.

Intradural Extramedullary Nerve Sheath Myxoma of the Cervical Spine: A Case Report and Review of Literature

Background: Nerve sheath myxoma is a rare benign soft tissue tumor. Intraspinal nerve sheath myxomas are rare. Only 8 cases of intraspinal nerve sheath myxoma have been reported to date, and no case of nerve sheath myxoma has been reported in the cervical spinal canal. Herein, we reported the first case of intradural extramedullary nerve sheath myxoma in the cervical spinal canal of a 57-year-old man, including its complete clinical course and radiological findings.

Case Presentation: A 57-year-old male patient presented with numbness in his left finger without any obvious inducement for 3 years. CT and contrast-enhanced magnetic resonance imaging (MRI) of the spine were performed. Based on the radiological examinations, a diagnosis of schwannoma was initially made. However, nerve sheath myxoma was finally confirmed by histopathological and immunohistochemical examinations. Complete tumor excision at the C1-2 level was performed. Then, the patient recovered well, and the numbness of his left finger disappeared during the later follow-up after the surgery.

Conclusion: Nerve sheath myxoma should receive diagnostic consideration for an extramedullary subdural lesion that is a clear boundary mass characterized by isointensity on T1-weighted images, heterogeneous intensity on T2-weighted images, obvious peripheral enhancement, and a growing tendency toward the intervertebral foramen.

Methylation-based classification of benign and malignant peripheral nerve sheath tumors

The vast majority of peripheral nerve sheath tumors derive from the Schwann cell lineage and comprise diverse histological entities ranging from benign schwannomas and neurofibromas to high-grade malignant peripheral nerve sheath tumors (MPNST), each with several variants. There is increasing evidence for methylation profiling being able to delineate biologically relevant tumor groups even within the same cellular lineage. Therefore, we used DNA methylation arrays for methylome- and chromosomal profile-based characterization of 171 peripheral nerve sheath tumors. We analyzed 28 conventional high-grade MPNST, three malignant Triton tumors, six low-grade MPNST, four epithelioid MPNST, 33 neurofibromas (15 dermal, 8 intraneural, 10 plexiform), six atypical neurofibromas, 43 schwannomas (including 5 NF2 and 5 schwannomatosis associated cases), 11 cellular schwannomas, 10 melanotic schwannomas, 7 neurofibroma/schwannoma hybrid tumors, 10 nerve sheath myxomas and 10 ganglioneuromas. Schwannomas formed different epigenomic subgroups including a vestibular schwannoma subgroup. Cellular schwannomas were not distinct from conventional schwannomas. Nerve sheath myxomas and neurofibroma/schwannoma hybrid tumors were most similar to schwannomas. Dermal, intraneural and plexiform neurofibromas as well as ganglioneuromas all showed distinct methylation profiles. Atypical neurofibromas and low-grade MPNST were indistinguishable with a common methylation profile and frequent losses of CDKN2A. Epigenomic analysis finds two groups of conventional high-grade MPNST sharing a frequent loss of neurofibromin. The larger of the two groups shows an additional loss of trimethylation of histone H3 at lysine 27 (H3K27me3). The smaller one retains H3K27me3 and is found in spinal locations. Sporadic MPNST with retained neurofibromin expression did not form an epigenetic group and most cases could be reclassified as cellular schwannomas or soft tissue sarcomas. Widespread immunohistochemical loss of H3K27me3 was exclusively seen in MPNST of the main methylation cluster, which defines it as an additional useful marker for the differentiation of cellular schwannoma and MPNST.

Intradural extramedullary myxoma at the L1 level

Myxoma of the peripheral nerve sheath is a rare benign tumor with predominant localization in the upper extremities, head, neck, and chest. In this study, we reported a clinical case of a patient with intradural myxoma at the L1 level. Much attention was given to histological characterization of the tumor and differential diagnosis of histological types of benign extramedullary tumors. A conclusion was drawn that patients with myxoma need further thorough examination as there is a risk of generalization of tumor process.