Pathology of Nerve Sheath Myxoma

Dr Sampurna Roy MD                    

Nerve sheath myxoma is a benign soft tissue tumour.

In 1969 Harkin and Reed described an unusual myxoid tumour of probable nerve sheath origin and named it myxoma of nerve sheath.

Later in 1980, Gallager and Helwig described similar lesions as Neurothekeoma.

Cellular neurothekeoma was described by Barnhill and Mihm in 1990.

Recent gene studies strongly supports that, nerve sheath myxomas and neurothekeoma are distinct neoplasms.

Schwann-cell differentiation in the electron microscopic examination of Nerve sheath myxoma cells, suggests an origin from nerve sheath precursor cells.

However, there are still some theories proposing a proliferation of other perineural cells, which brings controversies to the cell of origin.

There are some similar features of Nerve sheath myxoma with other neural tissue tumors, like schwannoma and neurofibroma.

That seems the reason why various names such as pacinian neurofibroma, cutaneous lobular neurofibroma and perineural neurofibroma have been used for this lesion.

Ref: Malkoc M, Ormeci T, Keskinbora M, Yılmaz A, Korkmaz O, Tanik CB. Nerve sheath myxoma of the dorsal paravertebral space. International Journal of Surgery Case Reports. 2014;5(11):858-860. doi:10.1016/j.ijscr.2014.10.003.

Age: Nerve sheath myxoma is usually noted in adolescents and young adults.

Site:  These myxoid lesions are more common on the trunk and lower extremities. Cellular lesions are noted on the head and neck and upper extremities. Some rare cases have been reported in the intracranial, spinal canal, trunk, lower limb and oral cavity.

Clinical presentation: Dome shaped nodule less than 3 cm in diameter. 

Microscopic features:

Nonencapsulated, multilobulated and hypocellular tumour, usually located in the reticular dermis and often extends into the subcutaneous fat. 

Tumour is composed of spindle cells, stellate and sometimes epithelioid cells set in a myxoid stroma.   

Spindle cells are arranged in swirling and concentric fashion.

Sometimes multinucleate cells are present.

Focally, there may be nuclear atypia and normal mitotic figures are often present.

Rarely, foci of  ossification and cartilaginous metaplasia have been reported.

Immunohistochemically, the tumour is S100 protein positive.

Differential Diagnosis: Myxoid Tumours of Soft Tissue : The differential diagnoses include schwannoma, neurofibroma, neurilemmoma, leiomyoma, intramuscular myxoma and low-grade sarcoma.

Nerve Sheath Myxoma - Pathology Infographics

Malkoc M, Ormeci T, Keskinbora M, Yılmaz A, Korkmaz O, Tanik CB. Nerve sheath myxoma of the dorsal paravertebral space. International Journal of Surgery Case Reports. 2014;5(11):858-860. doi:10.1016/j.ijscr.2014.10.003.

The "neurothekeoma": immunohistochemical analysis distinguishes the true nerve sheath myxoma from its mimics.

Histologic spectrum of neurothekeoma and the value of immunoperoxidase staining for S-100 protein in distinguishing it from melanoma. 

Studies on the cellular origin of neurothekeoma: clinical, light microscopic, immunohistochemical, and ultrastructural observations. 

Neurothekeoma: report of a case in an infant and review of the literature.