Answer of Dermatopathology Case 88

Neurothekeoma (Nerve Sheath Myxoma)

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Abstract:

Nerve sheath myxoma with bidirectional schwannomatous and perineural differentiation. Cesk Patol.2010 Jul;46(3):73-6.
A case of nerve sheath myxoma occurring in occipital region in 70-yr-old woman is presented. The tumor showed typical lobular and myxoid morphology. Immunohistochemically, it showed unusual coexpression of Schwann cell markers S100 protein and GFAP with perineural cell markers EMA and claudin-1. CD34+ fibroblast-like cells were scarce, and nerve axons were not found in the tumor. Clinical pathology and histogenesis of the lesion are discussed.

Nerve sheath myxoma (neurothekeoma) of the gingiva, a case report and review of the literature. Head Neck Pathol. 2010 Sep;4(3):242-5. Epub 2010 May 26.
Nerve sheath myxoma (NSM) is a benign peripheral nerve sheath tumor that rarely occurs in the oral cavity. Among the 23 reported intraoral cases, no lesion has previously been reported on the gingiva. In this report, we describe the first gingival case of oral neurothekeoma with histopathologic and immunohistochemical characteristics. The patient, a 32 year old female presented with a slowly growing gingival mass diagnosed clinically as an epulis. The lesion was surgically excised. Histopathologically, the lesion presented as a submucosal multinodular mass composed of spindle and stellate-shaped cells with a myxoid background. Immunohistochemically, the tumor cells were sporadically positive for S-100 and NSE and negative for GFAP, EMA, SMA, CD68 and HMB45. The immunoprofile of this lesion confirmed a Schwann cell origin. The lesion was followed up for 10 months with no reports of recurrence.

Neurothekeoma palpebrae: A report of 3 cases. Am J Dermatopathol. 2010 Jun;32(4):374-9.
Neurothekeoma palpebrae is the diagnostic term used to describe nerve sheath myxoma or neurothekeoma of the eyelid. Although these tumors are not uncommonly found in the head and neck region, eyelid involvement is very uncommon. We present 2 cases of cellular neurothekeoma and 1 case of nerve sheath myxoma occurring in the eyelid. Patient 1 was a 13-year-old girl with a left upper eyelid lesion of 6-months duration. Microscopic examination disclosed a cellular neurothekeoma with mild myxoid change and osteoclast-like multinucleated cells. Tumor cells infiltrated the orbicularis oculi muscle. The tumor cells were immunopositive for NKI.C3, CD34, and focally for S-100 protein. Multinucleated cells were reactive to CD68. Mart-1, smooth muscle actin, CD31, keratin, desmin, myogenin, synaptophysin, and neurofilament protein (NFP) were negative. Patient 2 was a 4-year-old girl with a left upper eyelid lesion diagnosed clinically as a chalazion. The lesion was incised. Five months later, the patient returned with a firm 5.5-mm nodule at the site. Excision revealed cellular neurothekeoma invading the orbicularis oculi. Tumor cells were NKI.C3 immunopositive and S-100 protein negative, and the multinucleated cells were CD68 positive. Patient 3 was a 70-year-old woman with a 10-year history of a subcutaneous right lower eyelid nodule which had recently changed color. The excised specimen demonstrated a hypocellular, well-circumscribed myxoid tumor surrounded by a thin rim of fibrous connective tissue. Tumor cells contained moderate amounts of eosinophilic cytoplasm with irregular, hyperchromatic nuclei. Nucleoli and mitotic figures were not apparent. Tumor cells were NKI.C3 negative, and S100 protein and glial acidic fibrillary protein positive, consistent with a nerve sheath myxoma. Including our 3 cases, 10 cases of nerve sheath myxoma and neurothekeoma occurring in the eyelid have been reported the English language literature. Although uncommon, these lesions should be kept in the differential diagnosis of eyelid tumors that can masquerade as chalazia.

Neurothekeoma: an analysis of 178 tumors with detailed immunohistochemical data and long-term patient follow-up information. Am J Surg Pathol. 2007 Jul;31(7):1103-14.
This report describes the clinicopathologic findings in 176 patients who presented with 178 tumors currently referred to as neurothekeomas. Our study group included 64 males and 112 females, ranging from 20 months to 85 years old at the time of their first surgical procedure (median age: 17 y). Twenty-four percent of patients were or=30 years of age at initial diagnosis. The patients typically presented with a solitary, superficial, slow-growing, and relatively asymptomatic mass in the 0.3 to 2.0 cm size range. One patient had multiple tumors. More than 75% of the lesions involved the head (n=63), upper extremities (n=44), and shoulder girdle (n=27) regions. The tumors were evident a few weeks to 4 years (median duration: approximately 7 mo) before surgical resection was sought. Histologically, the lesions involved the dermis and/or subcutis, and they formed multinodular masses with varying amounts of myxoid matrix and peripheral fibrosis. On the basis of the amount of myxoid matrix, the tumors were subclassified as cellular (n=63), mixed (n=67), or myxoid (n=48). All cases had spindled and epithelioid mononuclear neoplastic cells with relatively abundant cytoplasm and indistinct cell borders. The majority of cases also had occasional multinucleated tumor cells. The lesional cells had a strong tendency for whorled growth, and oftentimes, focal fascicular growth was also present. Nuclear atypia was minimal in 62 cases, mild in 73 cases, at least focally moderate in 41 cases, and focally marked in 2 cases. Mitotic activity ranged from 0 to 124 mitotic figures/25 wide-field high power fields (WHPFs) (median mitotic count: 4 mitotic figures/25WHPFs). Twenty-five lesions had >10 mitotic figures/25WHPFs. A total of 16 cases (9%) had atypical mitotic figures. Osteoclastlike giant cells were detected in 39% of cases. Immunoreactivity was typically present for vimentin, NKI/C3, CD10, microphthalmia transcription factor, and PGP9.5, and focal reactivity was sometimes noted for smooth muscle actin and CD68. All tumors tested were negative for S100 protein, glial fibrillary acidic protein, and Melan A. The overwhelming majority of cases had involvement of the tissue margins. A complete follow-up record is available for 71 patients (40.3%) with follow-up intervals ranging from 3 years 2 months to 34 years 9 months (median: 17 y 9 mo). Limited or incomplete follow-up information is also available for an additional 14 patients with follow-up intervals ranging from weeks to approximately 10 years (median: 5 mo). Regrowth of tumor after biopsy or local excision was reported in 13 patients, one of whom had 2 recurrences. However, because of the nature of our consultation practice and a tendency for clinicians to specifically send us cases with a complex clinical course, this is believed an overestimation of the true recurrence rate. Neurothekeomas are morphologically and immunohistochemically distinct from true nerve sheath myxomas. An origin from fibroblastic cells with the ability to differentiate into myofibroblasts and a tendency to recruit histiocytic cells is postulated.