[Clinicopathologic features of dermal nerve sheath myxoma and neurothekeoma: a comparative study].

Objective: To investigate the clinicopathologic characteristics and differential diagnosis of dermal nerve sheath myxoma (DNSM) and neurothekeoma (NTK). Methods: Clinical, pathological features and immunohistochemical profiles in 9 cases of DNSM and 8 cases of NTK were comparatively studied. The literature was reviewed. Results: The involved site of 9 DNSMs included the hand/fingers (n=3), ear (n=2), face, back, abdominal wall and waist (1 case each). Two of 8 NTKs arose in the forearm (n=2), one each in the nose, lip, shoulder, supraclavicular region, leg and hand. The most common presentation was a painless cutaneous nodule or plaque which grew slowly. Grossly, DNSM was often gelatinous, whereas NTK appeared relatively solid. Microscopically, both tumors were located in the dermis and/or subcutis. DNSM was composed of well-defined multiple lobules separated by fibrous septa. NTK also exhibited lobular or multinodular architecture, but was relatively ill-defined. Besides, fascicular or whorl-like arrangement was present in 3 cases of NTK. The lobules in DNSM consisted of a paucicellular proliferation of spindled, stellate and epithelioid cells forming interconnecting cords within abundant myxoid matrix. Small syncytial-like aggregates were readily noted. The constituted neoplastic cells in NTK were composed of ovoid to round epithelioid or histiocytoid cells. Scattered multinucleated giant cells were present in 2 cases. Based on the amount of myxoid matrix, 8 NTKs were further classified into cellular (5 cases), mixed (2 cases) and myxoid (1 case). By immunohistochemistry, neoplastic cells in DNSM were diffusely positive for S-100 protein, CD68, glial fibrillary acidic protein and SOX10, whereas neoplastic cells in NTK consistently expressed CD10 and microphthalmia transcription factor, with negativity for S-100 protein and SOX10. One patient each with DNSM and NTK experienced local recurrence due to incomplete excision. Conclusions: Although DNSM and NTK share clinical and pathological features, they belong to different entities. Whereas the former is consistent with a peripheral nerve sheath tumor, the latter is more akin to fibrous histiocytic tumor. Familiarity with their cliniopathologic characteristics and distinctive immunophenotypes will help distinguishing these two entities, as well as in the differential diagnosis of cutaneous neoplasms with similar features.

Benign cutaneous biphasic hybrid tumor of perineurioma and cellular neurothekeoma: A case report expanding the clinical and histopathologic features of a recently described entity.

Benign cutaneous plexiform hybrid tumor of perineurioma and cellular neurothekeoma (BCPHTPCN) is a recently described entity that presents as a solitary papule in the perioral area. As implied by its name, BCPHTPCN displays microscopic features of both perineurioma and cellular neurothekeoma arranged in a plexiform pattern. We report a case of nonplexiform benign cutaneous biphasic hybrid tumor of perineurioma and cellular neurothekeoma in a 36-year-old woman, who presented with a 4-year history of a firm, flesh-colored left ankle nodule. Histologically, there was a biphasic, well-circumscribed unencapsulated dermal mesenchymal proliferation with no connection to the epidermis, which exhibited mild acanthosis with slightly pigmented basal keratinocytes and overlying parakeratosis. The proliferation consisted of uniform bland spindle cells with bipolar cytoplasmic processes arranged in whorls with interspersed islands of epithelioid cells. Immunohistochemically, the spindle cell component was positive for CD34, EMA, and GLUT-1, consistent with perineurial differentiation, whereas the epithelioid nests were positive for NKI/C3 and MiTF, as expected in neurothekeoma. Stains for S100 protein, SOX10, desmin, claudin, pan-melanoma markers, and NSE were negative. We believe this case expands the histopathologic spectrum of BCPHTPCN showing that it can be grown in a nonplexiform pattern, and we suggest the term benign cutaneous biphasic hybrid tumor of perineurioma and cellular neurothekeoma as a more precise name. It is also, to the best of our knowledge, the first case reported outside the head and neck area.

Erythematous nodular lesion on the chest of an infant.

An 11-month-old girl presented with an erythematous nodule on the chest, which had been growing for 8 months. The tumor was composed of uniform polygonal and spindle-shaped cells, forming nodules and fascicles. The diagnosis of neurothekeoma was based upon the histology and immunohistochemistry.

[Nerve sheath myxoma of the hyponychium]. / Myxome des gaines nerveuses de l'hyponychium.

BACKGROUND: Nerve sheath myxoma is a rare benign tumour of the extremities that was long confounded with neurothekeoma. Herein, we describe a rare case of interest because of its site on the hyponychium. PATIENTS AND METHODS: A 31-year-old woman presented with a painless distal tumour on the right ring finger that had been present for 3 to 4 years. It consisted of a firm, round nodule under the nail and spreading to the fingertip. Complete excision was carried out after cutting away the distal nail plate. Histological examination revealed a myxoid tumour comprising very clearly delineated lobules containing pale fusiform cells with small nuclear inclusions. These cells expressed S100 protein but no CD34 or epithelial membrane antigen (EMA). Complete excision was performed and a full recovery was made. DISCUSSION: This type of tumour is characteristic of nerve sheath myxoma, and is almost certainly of Schwannian origin, although distinct from Schwannoma. It is rare, occurs after the age of 35 years and is preferentially located in the extremities of the limbs. There has only been one other description of its occurrence under the fingernail, in which it was described as neurothekeoma. However, neurothekeoma is entirely different, being more cellular, with no expression of protein S100, and marked by the NKIC3 antibody; it occurs in children or young adults, and is frequently found on the face. These two tumours were confused for some time, but today they must be completely distinguished from one another. These myxomas must be completely excised because of the risk of relapse. Finally, they should be distinguished from other myxoid tumours of the digits, certain of which can be malignant.

Orbital nerve sheath myxoma: a case report.

A 72-year-old man was referred to the Service of Ophthalmology due to a 2-year history of ptosis and a painless mass in the lateral orbital margin of the right eye. Orbital MRI revealed a well-demarcated lesion in the superotemporal quadrant of the orbit. After surgical excision, histopathological examination led to the diagnosis of nerve sheath myxoma, a tumor composed of myxoid nodules separated by fibrous septa with spindle-shaped and stellate cells. Many of these cells were immunostained with antibodies to S-100 protein. This is the first case reported in the literature of such a tumor located in the orbit, and, though extremely rare, it should be considered in the differential diagnosis of orbital tumors.

Classic neurothekeoma (nerve sheath myxoma) and cellular neurothekeoma of the oral mucosa: immunohistochemical profiles.

BACKGROUND: Classic neurothekeoma (nerve sheath myxoma) is regarded as being a true benign cutaneous tumor of nerve sheath origin. Cellular neurothekeoma was separated from the classic type by histogenesis, morphology and immunophenotype. Whether cellular neurothekeoma represents a continuum within the spectrum of classic neurothekeoma or is an independent entity is controversial. Only a small number of classic neurothekeomas of the oral mucosa have been reported and there are even fewer publications on cellular neurothekeoma. We analyzed a series of oral neurothekeomas (classic and cellular) with a panel of neural and other mesenchymal markers to enhance their diagnosis and classification. METHODS: One cellular and three classic neurothekeomas were submitted to a panel of immunohistochemical stains with antibodies against S100, S100A6, NSE, NKI/C3, PGP9.5, α-SMA, HHF-35, CD68 and vimentin. Two cases of neurofibroma (plexiform type), representing a true lesion of neural origin, served as control. RESULTS: The cellular neurothekeoma yielded a positive immunoreaction for S100A6 and NKI/C3 and a negative immunoreaction for S-100. The classic neurothekeomas demonstrated a positive reaction for S-100 and S100A6, but a negative one for NKI/C3. Other markers were non-contributory to distinguishing between these types of lesions. CONCLUSIONS: The small number of reported oral neurothekeomas (classic and cellular) could be due, in part, to the lack of recognition of their particular morphologic and immunohistochemical features. Our results indicate that testing for NKI/C3 immunoreactivity may be of value in distinguishing between cellular and classic neurothekeoma.

Multiple desmoplastic cellular neurothekeomas localized to the face of a 16-year-old boy.

Cellular neurothekeomas are relative uncommon benign dermal tumors of uncertain histogenesis. Most commonly they arise as a solitary papule or nodule on the head and neck or upper trunk of young adults with a slight female predominance. There has been only 1 previous report of multiple neurothekeomas. The patient described herein was a 16-year-old otherwise healthy boy who presented with approximately 30 facial papules that arose over the course of 6 months and progressively enlarged. Histologically, all lesions were composed of spindled to epithelioid cells, but varied in the degree of cellularity and dermal sclerosis. Immunohistochemical staining showed that the cells of interest expressed S100A6, vimentin, CD63 (NKI/C3), PGP 9.5, and factor XIIIa and were negative for CD68, glial fibrillary acid protein (GFAP), S-100, HMB-45, epithelial membrane antigen, actin, and CD57 consistent with a diagnosis of multiple desmoplastic cellular neurothekeomas.

Nerve sheath myxoma with bidirectional schwannomatous and perineural differentiation.

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.

Eyebrow papule in an elderly man.

A 70-year-old Caucasian man presented with a several-month history of a solitary, asymptomatic papule on the left eyebrow. His medical history included stage 1A lentigo maligna melanoma and multiple non-melanoma skin cancers. Physical examination demonstrated a solitary 5-mm smooth, dome-shaped skin colored papule with subtle central erosion on the left eyebrow. No overlying telangiectasias were noted. A biopsy of the lesion was performed. The lesion was composed of plump spindle cells arranged in a plexiform pattern in the background of thick, keloidal collagen bundles. The lesional cells were NKI/C3-positive and S-100-negative. A diagnosis of cellular neurothekeoma was made.

Myxoid neurothekeoma--a painful case in a less common location.

Myxoid neurothekeoma is a rare benign asymptomatic tumor of the skin. Most tumors are located on the head, shoulders and arms. We present a 19-year-old female patient with a relapsing tumor of this type in a less common localization, i.e., lower trunk, and with painful sensations under mechanical pressure. Wide excision surgery led to complete remission.

Nerve sheath myxoma (neurothekeoma) arising in the oral cavity: histological and immunohistochemical features of 3 cases.

This report describes the histological and immunohistochemical characteristics of 3 cases of nerve sheath myxoma (NSM)/neurothekeoma arising in the oral cavity. Histopathologically, 3 distinct variants were observed based on the amount of myxoid matrix: classic/hypocellular, cellular, and mixed types. Immunohistochemically, all types expressed strong immunoreactivity to S-100 protein (3/3), NSE (neuron-specific enolase) (3/3), and NGFR (nerve growth factor receptor) (3/3), whereas all cases were negative for SMA (smooth muscle actin) and FVIII. The number of Ki-67 positive cells was less than 5% in all lesions confirming the slow growing characteristics of NSM. The results suggest that NSMs of the oral cavity are true peripheral nerve sheath tumors and show close relationship to schwannoma.

Neurothekeoma of the eyelid: a case report.

The purpose of this article is to describe a rare benign tumor of nerve sheath origin arising from the eyelid in an elderly male. Local excision was done and histopathological examination revealed a neurothekeoma. Six months later the patient was doing well with no recurrence. The case was unique in that the patient was an elderly male while neurothekeoma is commonly seen on the face of young adults, especially females.

Neurothekeoma: an analysis of 178 tumors with detailed immunohistochemical data and long-term patient follow-up information.

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.

Unusual benign myxoid nerve sheath lesion: myxoid palisaded encapsulated neuroma (PEN) or nerve sheath myxoma with PEN/PEN-like features?

A 38-year-old woman had a polypoid nodule on her scalp. The lesion histopathologically demonstrated an extensive myxoid lobular lesion associated with a nonmyxoid and cellular area in the peripheral area of the lesion. The features of the peripheral cellular area resembled those of palisaded encapsulated neuroma (PEN). Most of the lesion was myxoid, with a large lobule in which several thin fibrous septa were present, dividing it into smaller lobules. The myxomatous area was composed of spindle cells or stellate cells with elongated cytoplasmic processes. There was a loose cellular network with a reticular and netlike network pattern or a lamellar pattern. From the immunohistochemical findings, as well as the histopathologic features, the whole lesion was thus considered to be a PEN, whereas the main, myxoid, lobular lesion was thought to have been caused by myxoid changes within a PEN, namely, myxoid PEN. It cannot be completely ruled out, however, that this case could be that of a nerve sheath myxoma with a PEN/PEN-like lesion. Thus, the present case may suggest that PEN can show extensive myxoid change or may demonstrate a relationship between PEN and nerve sheath myxoma.

Cellular neurothekeoma with a plexiform morphology: a case report with a discussion of the plexiform lesions of the skin.

Neurothekeoma is a rare benign dermal lesion that is commonly seen in children and teenagers. Despite its name, the true nature of this lesion is uncertain and controversial, particularly after the emergence of the cellular (spindle/epithelioid) variant. We describe the histological and immunohistochemical findings of a right thigh skin lesion in an 11-year-old girl. It consists of a dermal ill-defined plexiform mass composed of nests and fascicles of spindle cells with pale eosinophilic cytoplasm that lie within a sclerotic stroma. The immunohistochemistry shows diffuse reactivity to CD68, matrix metalloproteinase-II, CD10 and PGP9.5 with focal reactivity to CD57 and CD34. The lesion is negative for S100, factor XIIIa, smooth muscle markers and melanocytic markers. The features are compatible with a cellular variant of neurothekeoma with plexiform pattern that also exhibits an unusual pattern of fibrohistiocytic phenotype. Although such a lesion is benign, it has a wide but important differential diagnoses that are reviewed briefly together with a brief discussion about the origin of this rare entity.

Cellular neurothekeoma: detailed characterization in a series of 133 cases.

Cellular neurothekeomas are distinctive benign cutaneous tumors of uncertain histogenesis. As relatively few cases have been reported, their clinical features and morphologic spectrum remain incompletely defined, and the significance of atypical histologic features is uncertain. This study examined the clinicopathologic and immunohistochemical features of 133 cellular neurothekeomas received between 1987 and 2003. There was a 1.8:1 female predominance, with a mean age of 25 years (84% <40 y). Mean tumor size was 1.1 cm (range: 0.3 to 6 cm; 90% <2 cm). The tumors arose most often on the upper limb (35%) or head and neck (33%). Fifty-two percent of the tumors were limited to the dermis, and 48% also involved superficial subcutaneous tissue. In 30% of cases, neurothekeoma was suggested by the referring pathologist; the most common other diagnoses offered were plexiform fibrohistiocytic tumor, benign fibrous histiocytoma, and a low-grade sarcoma. Histologically, most cases were poorly marginated; 33 (25%) infiltrated fat, and 10 (8%) entrapped skeletal muscle (all but 1 situated on the face). Nearly all tumors had a lobulated or micronodular architecture and were composed of nests and bundles of epithelioid to spindled cells with palely eosinophilic cytoplasm, often separated by dense hyaline collagen; 17 (13%) showed focally sheetlike areas, and 5 (4%) were notably plexiform. Myxoid stroma was observed in 38 (29%) tumors; 11 (8%) were predominantly myxoid. Five (4%) showed marked stromal hyalinization. Osteoclastic giant cells were seen in 20 (15%) cases. The mean mitotic rate was 3 per 10 high power fields; 28 (21%) had > or =5 per 10 high power fields. Most tumors showed mild cytologic atypia in the form of nuclear variability and small nucleoli; 33 (25%) contained notably pleomorphic cells. All tumors were reactive for NKI-C3, 110/123 (89%) expressed neuron-specific enolase, 73/127 (57%) showed at least focal staining for smooth muscle actin, and only 1 was focally desmin positive. All tumors were negative for S-100 protein. Follow-up ranged from 5 to 146 months (mean 44 mo). Ten tumors recurred locally (7 situated on the face), after a mean of 18 months; tumor had been marginally excised or had involved excision margins in all cases with available information. No other clinical or pathologic features correlated with recurrence. Cellular neurothekeomas have a predilection for the upper limbs and head and neck of pediatric and young adult females and rarely recur following incomplete excision. There is no good evidence that these lesions show nerve sheath differentiation and the nomenclature will likely change when the tumor cell lineage is better defined. Atypical histologic features (including pleomorphism, infiltration of subcutis, and a high mitotic rate) seem to have no clinical significance.

Frequent positive staining with NKI/C3 in normal and neoplastic tissues limits its usefulness in the diagnosis of cellular neurothekeoma.

NKI/C3 originally was described as a marker for melanoma. Recently, it resurfaced as a marker to separate cellular neurothekeoma from other dermal tumors in the differential diagnosis. To determine the sensitivity and specificity of NKI/C3, we evaluated its staining pattern in 709 normal and neoplastic tissues, including 92 dermal tumors, using tissue microarrays and conventional sections. We found that although NKI/C3 is positive in only a few normal tissues, it stains a broad spectrum of neoplastic tissues. NKI/C3 is also positive in many dermal tumors of possible histiocytic origin, including juvenile xanthogranuloma (6/10), atypical fibroxanthoma (4/12), cellular fibrous histiocytoma (5/10), reticulohistiocytoma (3/6), and xanthoma (8/10). However, it is negative in epithelioid cell histiocytomas (0/7) and Langerhans cell histiocytosis (0/9). Given the wide spectrum of positive staining in morphologic mimics of cellular neurothekeomas, pathologists should be cautious when making this diagnosis based solely on positive staining with NKI/C3.