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Year : 2017  |  Volume : 60  |  Issue : 4  |  Page : 610-611
Nerve sheath myxoma: Unusual location and a diagnostic pitfall


1 Department of Pathology, Yeungnam University College of Medicine, Daegu, South Korea
2 Department of Surgery, Yeungnam University College of Medicine, Daegu, South Korea

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Date of Web Publication12-Jan-2018
 

How to cite this article:
Kwon HJ, Kim JH, Choi JH, Gu MJ. Nerve sheath myxoma: Unusual location and a diagnostic pitfall. Indian J Pathol Microbiol 2017;60:610-1

How to cite this URL:
Kwon HJ, Kim JH, Choi JH, Gu MJ. Nerve sheath myxoma: Unusual location and a diagnostic pitfall. Indian J Pathol Microbiol [serial online] 2017 [cited 2019 Jun 20];60:610-1. Available from: http://www.ijpmonline.org/text.asp?2017/60/4/610/222968




Nerve sheath myxoma (NSM) is a slowly growing benign tumor with a peripheral nerve sheath origin. It was first described by Harkin and Reed in 1969.[1] NSM most often occurs in the extremities, but cases of occurrences in the head, intraspinal space, and breast have also been reported. Neurothekeoma and NSM were previously considered to be related neoplasms of peripheral nerve sheath origin. However, they are separate, distinct neoplasms with discrete gene expression profiles.[2] We report the first case of NSM with perianal presentation.

A 35-year-old man presented with a perianal mass, which he had had for 10 years. Two years previously, he had undergone a fistulectomy at a local clinic. However, he was suffering from perianal pain. Physical examination revealed tenderness in a subcutaneous lesion between the scrotum and the anus. The overlying skin was unremarkable.

On an anal ultrasonogram, the anal sphincter was observed to be intact and no fistula tract was found. There was a mass about 3 cm in dimension in the subcutaneous area. Excision was performed.

Gross examination of the specimen showed a well-demarcated mass that was 2.5 cm × 1.6 cm × 1.5 cm in size. Cut sections showed translucent, variably sized mucoid nodules with thin septum [Figure 1]. There was no solid area. Microscopic examination showed that the tumor was composed of variably sized, well-defined myxoid nodules, separated by fibrous septa [Figure 2]a. Spindle cells and stellate cells with cytoplasmic processes were embedded in myxoid stroma [Figure 2]b. There was neither nuclear atypia nor mitosis. The tumor cells were diffusely positive for S100 and glial fibrillary acidic protein (GFAP) and were negative for epithelial membrane antigen (EMA) and CD34 [Figure 3]a and [Figure 3]b.
Figure 1: Cut sections showing mucoid nodules that are well-demarcated, translucent, glistening, and variably sized mucoid nodules with thin septum

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Figure 2: Tumor composed of multiple myxoid nodules surrounded by fibrous septum (a: H and E, ×4) and spindled or stellate tumor cells are scattered in myxoid background (b: H and E, ×10)

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Figure 3: The spindled or stellate tumor cells showing positivity for S100 (a: ×10) and negativity for epithelial membrane antigen (b: ×10)

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Nerve sheath myxoma is a rare, benign, soft-tissue tumor that most often presents as a soft nodule in the extremities, especially the hands. It has a high local recurrence rate when incompletely excised. NSM was initially defined as a myxoid, loosely cellular and micronodular tumor of the neural origin by Harkin and Reed.[1] Since the initial definition of NSM, there have been considerable debates about its line of differentiation and relationship with neurothekeoma. However, recent studies revealed reproducible clinical, histopathological, immunohistochemical, and genetic differences between these two entities.[2],[3] Neurothekeoma occurs more common than NSM and usually presents as a solitary mass in the head and neck.[4] Sheth et al. suggested that NSMs have a peripheral nerve sheath origin and are distinct, separate tumors from neurothekeomas.[2] In contrast, neurothekeomas of all subtypes resemble cellular fibrous histiocytomas on gene expression profiling, originate from fibroblastic cells, and may be a variant of fibrous histiocytoma.[2],[3] Immunohistochemical results are also helpful for differential diagnosis. Neurothekeoma is positive for EMA and negative for S100 and GFAP. On the other hand, NSM is diffusely positive for S100 and GFAP and negative for EMA.

The histologic differential diagnosis of NSM includes other benign peripheral nerve sheath tumors and highly myxoid tumors.[4],[5] Myxoid neurofibroma occurs as poorly circumscribed, unencapsulated masses that lack lobular architecture and show patchy S-100 expression. Perineuriomas typically form distinctive whorled, fascicular growth patterns in the myxoid or collagenized stroma and are distinguished from NSM by their strong immunoreactivity for EMA and nonreactivity for S100, GFAP, and CD34. Myxoid schwannoma lacks multinodularity and shows Antoni A foci with Verocay bodies. Cutaneous myxoma forms myxoid multinodular masses in the dermis and subcutaneous lesions. The tumor cells are stellate or spindle-shaped, often have smudgy nuclear chromatin, and show negativity for S100 and reactivity for CD34.

Complete excision with a free tumor resection margin is a treatment of choice for NSM. Although malignant transformation has not been reported, close follow-up is recommended because of high local recurrence rates of up to 50%.[4]

We experienced an unusual perianal presentation of NSM and reviewed the relevant literatures. Although NSM is rare, it is important to differentiate this disease from other myxoid tumors and to be aware of its characteristics because of the high rate of local recurrence.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Harkin JC, Reed RJ. Tumors of the peripheral nervous system. In: Atlas of Tumor Pathology Series 2, Fascicle 3. Washington, DC: Armed Forces Institute of Pathology; 1969.  Back to cited text no. 1
    
2.
Sheth S, Li X, Binder S, Dry SM. Differential gene expression profiles of neurothekeomas and nerve sheath myxomas by microarray analysis. Mod Pathol 2011;24:343-54.  Back to cited text no. 2
    
3.
Fetsch JF, Laskin WB, Hallman JR, Lupton GP, Miettinen M. Neurothekeoma: An analysis of 178 tumors with detailed immunohistochemical data and long-term patient follow-up information. Am J Surg Pathol 2007;31:1103-14.  Back to cited text no. 3
    
4.
Bartake A, Palaskar SJ, Narang B, Kathuriya P. Nerve sheath myxoma of the oral cavity: A distinct entity. Br J Neurosurg 2017;10:1-2.  Back to cited text no. 4
    
5.
Safadi RA, Hellstein JW, Diab MM, Hammad HM. Nerve sheath myxoma (neurothekeoma) of the gingiva, a case report and review of the literature. Head Neck Pathol 2010;4:242-5.  Back to cited text no. 5
    

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Correspondence Address:
Mi Jin Gu
Department of Pathology, Yeungnam University College of Medicine, Daegu
South Korea
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJPM.IJPM_302_17

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  [Figure 1], [Figure 2], [Figure 3]



 

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