Dermal nerve sheath myxoma
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Dermal nerve sheath myxomas are benign peripheral nerve sheath tumors usually originating from the skin or subcutaneous tissues.
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The previous term was ‘classic or myxoid variant of neurothekeoma’ but recent data has shown that they are biologically and clinically distinct from neurothekeoma 1,2.
The diagnosis of dermal nerve sheath myxoma is established by a combination of clinical, histological and immunohistochemical features 1.
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:
- small superficial lesions of the distal extremities in young adult patients
- multilobulated myxoid neoplasm
- consisting of bland spindle cells and epithelioid Schwann cells
- immunoreactivity for S100
Dermal nerve sheath myxomas are rare tumors. They occur in a wide age range with a peak in the fourth decade of life. Men are slightly more frequently affected 1,4.
They are usually slow-growing and otherwise asymptomatic. Sometimes they can be painful 1.
Dermal nerve sheath myxomas are myxoid neoplasms with a multinodular growth pattern consisting of bland spindle cells and epithelioid Schwann cells 1.
The etiology is unknown 1.
Dermal nerve sheath myxomas are often found in the dermis and subcutis of extremities, in particular, the fingers knees and toes. They also can be rarely found around the spinal canal 1-3.
Macroscopically dermal nerve sheath myxomas are well-delineated shimmering white to translucent nodules of a firm to rubbery consistency. They have varying sizes on detection but most are small and less than 2.5 cm 1.
Histological features of dermal nerve sheath myxomas include the following 1-4:
- multinodular growth pattern
- abundant myxoid matrix surrounded by a prominent crust of fibrous tissue
- small epithelioid ring-like stellate or spindled neoplastic Schwann cells arranged in cords or nests
- mild nuclear atypia
- few mitoses
Neoplastic Schwann cells should be diffusely positive S100 and show reactivity to GFAP, and CD57 on immunohistochemistry stains. The surrounding fibrous connective tissue should respond to collagen IV 1-4.
On ultrasound, dermal nerve sheath myxomas have been described as lobulated and with a heterogeneous hyperechoic echotexture 4.
On MRI dermal nerve sheath myxomas have been described as a well-defined lesion with the following signal characteristics 4,5:
- T1: isointense compared to muscle
- T2: hyperintense
- T1 C+ (Gd): enhancement
The radiological report should include a description of the following:
- form, location and size
- tumor margins and transition zone
- relations to the muscular fascia
- relations to bones
- relations to neurovascular structures
Treatment and prognosis
Management of dermal nerve sheath myxomas usually consists of complete excision. However, they feature a high recurrence rate of up to 47% which can occur repeatedly 1.
History and etymology
Dermal nerve sheath myxomas were first reported in the literature by two American pathologists, James C. Harkin and Richard Jay Reed in 1969 2,3,6.
Tumors or conditions which can mimic the presentation and/or appearance of dermal nerve sheath myxomas include:
- cellular neurothekeoma: more common in the head and neck area
- acral fibromyxoma: often near the nailbed
- plexiform neurofibroma: often associated with neurofibromatosis type 1
- 1. Dry SM. Dermal nerve sheath myxoma. In: WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours. Lyon (France): International Agency for Research on Cancer; 2020. (WHO classification of tumours series, 5th ed.; vol. 3). https://publications.iarc.fr
- 2. Sheth S, Li X, Binder S, Dry S. Differential Gene Expression Profiles of Neurothekeomas and Nerve Sheath Myxomas by Microarray Analysis. Mod Pathol. 2011;24(3):343-54. doi:10.1038/modpathol.2010.203 - Pubmed
- 3. Fathaddin A & Fatani R. Palmar Nerve Sheath Myxoma: A Case Report. Oman Med J. 2012;27(3):e035. doi:10.5001/omj.2012.64 - Pubmed
- 4. Malkoc M, Ormeci T, Keskinbora M, Yılmaz A, Korkmaz O, Tanik C. Nerve Sheath Myxoma of the Dorsal Paravertebral Space. Int J Surg Case Rep. 2014;5(11):858-60. doi:10.1016/j.ijscr.2014.10.003 - Pubmed
- 5. Khashaba H, Hafez E, Burezq H. Nerve Sheath Myxoma: A Rare Tumor, a Case Report and Literature Review. Int J Surg Case Rep. 2020;73:183-6. doi:10.1016/j.ijscr.2020.07.030 - Pubmed
- 6. Harkin JC, Reed RJ. Tumors of the Peripheral Nervous System. AFIP - Atlas of Tumor Pathology - 2nd Edition. 1969; 3:29-65.