Cellular 'neurothekeoma': an epithelioid variant of dermatofibroma?

Protein gene product 9.5 (PGP9.5) expression in benign cutaneous mesenchymal, histiocytic, and melanocytic lesions: comparison with cellular neurothekeoma

Cellular neurothekeoma (CNTK) frequently enters the differential diagnosis of a benign dermal cellular proliferation. Diagnosis often relies on immunohistochemistry including the use of protein gene product 9.5 (PGP9.5). A previous study demonstrated PGP9.5 expression across a wide variety of soft tissue neoplasms. We explored the utility of this antibody in distinguishing CNTK from other benign dermal-based lesions. A cohort of CNTK (n=7) and benign cutaneous lesions of neural (n=28), fibrohistiocytic (n=23), fibroblastic (n=25), histiocytic (n=18), myofibroblastic (n=7), smooth muscle (n=14), and melanocytic (n=12) differentiations were immunostained with PGP9.5. Staining was graded by H-score and compared with CNTK. A significantly higher H-score was found in CNTK compared with the fibrohistiocytic (p=0.0001), histiocytic (p=0.0016), myofibroblastic (p=0.0003), smooth muscle (p<0.0001), and melanocytic (p=0.0004) groups, with the exceptions of plexiform fibrohistiocytic tumour, xanthoma, and xanthogranuloma. No significant difference was found when comparing CNTK with fibroblastic and neural lesions, with the exceptions of neurofibroma and perineurioma. In conclusion, PGP9.5 is helpful in distinguishing CNTK from most benign cutaneous fibrohistiocytic, histiocytic, myofibroblastic, smooth muscle, and melanocytic lesions. In addition to CNTK and neural lesions, PGP9.5 is also expressed in benign fibroblastic lesions, and therefore distinction of these lesions should not be based on PGP9.5 positivity.

Cellular Neurothekeoma: A Rare Tumor with a Common Clinical Presentation

Neurothekeomas are rare benign tumors commonly found on the head, neck, and upper extremities of women and younger individuals. They are thought to be of nerve sheath origin and usually present as painless, slow growing masses. We present a case of cellular neurothekeoma on the nasal ala of an 8-year-old girl with no previous history of trauma or piercings. Differential diagnosis, treatment options, and special considerations regarding potentially atypical characteristics are discussed.

Dermatofibroma—A Critical Evaluation

Dermatofibromas are common cutaneous lesions. In most cases, they can be readily identified clinically and show a typical histology. In a small percentage of cases they show unusual clinical and more often histologic features that may cause differential diagnostic problems. In addition there are reactive fibrous lesions with neural or smooth muscle features that we speculate may represent dermatofibroma variants.

Cellular neurothekeoma: analysis of 37 cases emphasizing atypical histologic features

Cellular neurothekeoma is a frequent source of diagnostic difficulty. In order to gain more insight into the range of histologic features of cellular neurothekeoma, we examined all cases from our institution, with a focus on describing atypical histologic features. Cases with sufficient histologic material for evaluation were retrieved. Cases were analyzed for demographics, growth pattern, myxoid stroma, cytologic atypia, mitotic rate, perineural invasion, and other histologic features. The 37 patients (16 M; 21 F) had a mean age of 31.0 years (range: 4-89). Tumors involved the head and neck (n=16), arms (n=11), trunk and shoulders (n=8), and foot (n=2). All cases had at least focal nesting of epithelioid to spindled tumors cells characteristic of cellular neurothekeoma. In many, alternate growth patterns were present and represented the dominant pattern in some. These patterns included fascicular (n=9), sheet-like (n=6), and corded (n=4). Myxoid stroma was present in 14 and was prominent in 5. Cytologic atypia was present in 19 patients, with 3 having severe atypia. Mean mitotic rate was 2.0/mm(2) (range 0-10 per mm(2)). Neurotropism was seen in four cases. Other unusual features included collagen trapping, giant cells, hemorrhage, lymphocytic cuffing, chondroid stroma, and cellular vacuolization. Cellular neurothekeoma has a wider range of features than is commonly recognized. The presence of nests of epithelioid tumor cells with characteristic cytologic features, no matter how focal, is a clue to the diagnosis.

SOX-10 and MiTF expression in cellular and 'mixed' neurothekeoma

BACKGROUND

Neurothekeoma and nerve sheath myxoma have long been interpreted as related tumors that share nerve sheath linage. Lack of S100 expression in neurothekeoma and similarities of gene expression profiles between neurothekeoma and fibrohistiocytic tumors have created reasonable doubt about this concept. SOX-10 represents a marker for schwannian and melanocytic differentiation, and is expressed in other tumors of nerve sheath linage. Microphthalmia transcription factor (MiTF) expression has been repeatedly reported in cellular neurothekeoma in the recent literature and was proposed as a helpful marker in this entity.

METHODS

We investigated 25 cases of cellular neurothekeoma, 8 cases of mixed neurothekeoma and 1 case of nerve sheath myxoma for the expression of SOX-10, MiTF, S100, NKI/C3, Melan-A and smooth muscle actin (SMA) using immunohistochemistry.

RESULTS

A lack of SOX-10 expression was demonstrated in 100% of cellular and mixed neurothekeomas, but was present in the case of nerve sheath myxoma. More than two thirds of neurothekeomas showed very focal or no reactivity with MiTF.

CONCLUSIONS

Our data suggest that neurothekeoma and nerve sheath myxoma are unrelated, and that cellular and mixed neurothekeoma may not be of nerve sheath lineage. In addition, MiTF should not be regarded as a useful marker in neurothekeoma.

A Case of a Cellular Neurothekeoma Presenting with Headaches and Review of the Literature

A 12-year-old female presented with a 1-year history of a slow-growing lesion on the frontal scalp. The patient reported intermittent headaches increasing in frequency localized under the lesion. Physical exam revealed a firm, fixed, 5-mm orange-pink papule on the right frontal scalp. Excisional biopsy was performed using a 6-mm punch biopsy, after which the patient reported a cessation of headaches. Histopathology showed a diffuse proliferation of spindled and epithelioid cells within the superficial and deep reticular dermis demonstrating a nested as well as fascicular growth pattern. There was also focal myxoid dermal change. Immunohistochemical staining showed the tumor to be strongly positive for NK1C3 and negative for S-100. A diagnosis of cellular neurothekeoma was made. Cellular neurothekeomas are slow-growing, asymptomatic nodules that most frequently appear on the head and neck of young adults. Cellular neurothekeomas rarely present with symptoms beyond mild tenderness upon palpation. Our case represents a unique presentation of a neurothekeoma of the scalp with complaint of headaches, previously unpublished in the literature.

Fibrohistiocytic tumors and related neoplasms in children and adolescents

Fibrohistiocytic tumors (FHTs) in children and adolescents range from the benign fibrous histiocytoma, or dermatofibroma, to a variety of intermediate and malignant neoplasms, such as dermatofibrosarcoma protruberans and high-grade undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma). Those tumors as a group are comprised of fibroblasts, myofibroblasts, and histiocytes-dendritic cells with a variably prominent inflammatory infiltrate consisting of lymphocytes and eosinophils. Dendritic cells are also a major constituent of another group of neoplasms that include Langerhans cell histiocytosis, follicular and interdigitating cell sarcomas, and juvenile xanthogranuloma. These latter tumors are considered in this discussion for the sake of differential diagnosis and their possible histogenetic relationship to FHTs. Recent studies have suggested that the relationship between the fibroblast and histiocyte in the FHTs may reflect the intrinsic capacity to transdifferentiate from one to the other morphologic and functional state. The so-called "facultative fibroblast," as a cell with fibroblastic and histiocytic properties, was discussed in the context of the fibrous xanthoma 50 years ago. Possibly the entire histogenetic concept of FHTs should be reconsidered in light of current studies.

Neurogenic tumors of soft tissue

Neurogenic tumors are an uncommon yet important category of soft tissue tumors in children and adolescents because of their frequent association with various genetic syndromes. The heterogeneous cellular composition of the peripheral nerve and the wide metaplastic capacity of the neural crest and its derivatives generate a variety of neoplasms with neurogenic differentiation. This article reviews the clinicopathologic features and differential diagnosis of neurogenic tumors in the first two decades of life, and highlights use of selected ancillary methods for diagnosis.

Differential gene expression profiles of neurothekeomas and nerve sheath myxomas by microarray analysis

Neurothekeomas and dermal nerve sheath myxomas have previously been considered related cutaneous neoplasms of peripheral nerve sheath origin based on light microscopic similarities. However, recent immunohistochemical and ultrastructural data indicate nerve sheath myxomas exhibit true nerve sheath differentiation, whereas no such compelling evidence exists for neurothekeomas. Although neurothekeomas lack a specific immunohistochemical profile, similar antigen expression and histopathologic patterns suggest neurothekeomas may be categorized as fibrohistiocytic tumors. To date, no known molecular studies have examined the histogenetic relationship of these tumors. We report the first microarray-based gene expression profile study of these entities on formalin-fixed paraffin-embedded tissues. Cases of dermal schwannomas, dermal nerve sheath myxomas, myxoid/mixed/cellular neurothekeomas, and cellular fibrous histiocytomas diagnosed in the past 3 years were identified in our database. Archival formalin-fixed paraffin-embedded tissue from 28 patients was selected for microarray analysis (seven schwannomas, five nerve sheath myxomas, nine myxoid/mixed/cellular neurothekeomas and seven cellular fibrous histiocytomas). Following tumor RNA isolation, amplification and labeling using commercially available kits, labeled targets were hybridized to the Affymetrix GeneChip Human Genome U133 Plus 2.0 Array (Santa Clara, CA, USA). Acquisition of array images and data analyses was performed using appropriate software. Hierarchical clustering and principal component analysis demonstrated discrete groups, which correlated with histopathologically identified diagnoses. Dermal nerve sheath myxomas demonstrate very similar molecular genetic signatures to dermal schwannomas, whereas neurothekeomas of all subtypes more closely resemble cellular fibrous histiocytomas. We are the first to report distinct gene expression profiles for nerve sheath myxomas and neurothekeomas, which further substantiates the argument that these are separate entities. Our molecular data confirms that dermal nerve sheath myxomas are of peripheral nerve sheath origin, and suggests that neurothekeomas may actually be a variant of fibrous histiocytomas.

Sclerotic epithelioid dermatofibroma

Dermatofibroma ("fibrous histiocytoma") is a common soft tissue lesion with many variants based on a great variety of architectural patterns, cellular morphology and stromal reactions. The coexistence of 2 or more patterns within a single lesion is well known and causes diagnostic difficulties. We report a case of an unusual histologic presentation of a solitary sclerotic and epithelioid dermatofibroma in a 48-year-old woman.

Recurring mixed-type neurothekeoma of the face

BACKGROUND

Neurothekeomas are rare, benign neoplasms, typically occurring in younger patients with a remarkable predilection for the female population. The nomenclature and derivation of these tumors is controversial. The rarity of this unusual skin tumor in daily routine histopathologic findings prompted the following report.

OBSERVATION

We report a 17-year-old girl with an asymptomatic nodule at the inner angle of the left eye with slow progression in size within 12 months to 1 cm in diameter. Multiple treatments with laser surgery were performed and yielded no persistent remission of the tumor. Histopathologic examination revealed a non-encapsulated dermal tumor, composed of multiple, closely situated medium-sized nodules, separated by a myxoid collagenrich stroma, without epidermal alteration. In summary, due to the histoarchitecture and immunoprofile of the tumor, a mixed-type cellular neurothekeoma was diagnosed.

CONCLUSION

We think that it is important to be aware of these uncommon soft tissue lesions and the pitfalls of mixed-type neurothekeomas that often cause diagnostic problems. The aim of this report is to help to avoid misdiagnoses of malignant mesenchymal tumors with serious consequences, including extensive surgical therapy or radiation.

Neurothekeoma palpebrae: A report of 3 cases

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.

A rare case of atypical cellular neurothekeoma in a 68-year-old woman

Cellular neurothekeoma is a benign dermal lesion of uncertain differentiation. The atypical variant of cellular neurothekeoma, characterized by features such as large size, deep penetration, diffusely infiltrative borders, vascular invasion, high mitotic rate and marked cytologic pleomorphism, has been very rarely reported in the literature. We present the clinical, histopathological and immunohistochemical profile of a new case of atypical cellular neurothekeoma in a 68-year-old female patient who was diagnosed with ductal breast carcinoma in situ before. An erythematous painless papule arose in her right breast, and tentative clinical diagnosis was orientated toward skin metastasis of breast cancer or fibroma. Upon histological examination, the lesion showed the histological and immunohistochemical features of atypical variant of cellular neurothekeoma with high mitotic rate, marked cellular pleomorphism and penetration into subcutaneous fat. A further unusual feature in our patient was her age, because she is the oldest patient reported in the literature with diagnosis of atypical cellular neurothekeoma so far. Prognosis remains uncertain because only few cases of atypical cellular neurothekeoma have been reported in the literature, with a very limited follow-up time. Our report contributes to a better characterization of the clinical and morphologic features of atypical cellular neurothekeoma.

An infiltrative variant of non-neural granular cell tumor: a case report

Dermal non-neural granular cell tumors are rare tumors of indeterminate lineage that typically present as well-circumscribed tumors with nuclear pleomorphism and mitotic activity. We describe a dermal non-neural granular cell tumor with a distinctive growth pattern with granular cells interspersed between collagen bundles. This asymptomatic papule arose on the scapula of a 46-year-old woman and consisted of a mixture of epithelioid and spindled granular cells. The immunohistochemical characteristics were similar to those of previously reported dermal non-neural granular cell tumors. Despite mild nuclear pleomorphism and dispersion of lesional cells among collagen bundles, mitoses were not present and Ki-67 staining indicated a low proliferative rate. In addition to being S-100 protein negative and NKI/C3 positive, our case was positive for PGP9.5 and weakly positive for neuron-specific enolase, a staining pattern similar to what has been observed for cellular neurothekeomas. Our case could represent a dermal non-neural granular cell tumor with unique architecture, a granular cellular neurothekeoma or a granular cell dermatofibroma. As both dermal non-neural granular cell tumor and cellular neurothekeoma are of indeterminate lineage, our case with features characteristic of both entities may suggest a common precursor or lineage for dermal non-neural granular cell tumor and cellular neurothekeoma.

Diagnostic value of CD163 in cutaneous spindle cell lesions

BACKGROUND

The histologic diagnosis of atypical fibroxanthoma (AFX) can sometimes be challenging. No specific marker exists to confirm the diagnosis other than excluding other entities. CD163 has been shown to have great specificity for tumors of monocyte/histiocyte lineage. In this study, we evaluated the diagnostic utility of CD163 in diagnosing AFX and in identifying skin lesions with histiocytic/dendritic derivation.

METHODS

A total of 157 cases, including 14 AFXs, 5 spindle cell squamous cell carcinomas (SCCs), and 7 spindle cell/desmoplastic melanomas, along with other cutaneous spindle cell and histiocytic/fibrohistiocytic lesions, were stained with CD163.

RESULTS

CD163 was expressed in 11 of 14 (79%) AFXs, with moderate to strong intensity. No staining was observed in cases of spindle cell SCC (0/5) and dermatofibrosarcoma protuberans (0/10). Rare spindle cell/desmoplastic melanomas (2/7) and cutaneous leiomyosarcomas (1/5) demonstrated positive staining. CD163 reactivity was seen in 24 of 29 of benign fibrous histiocytomas (BFHs), including 8 of 8 cellular fibrous histiocytomas and 6 of 9 epithelioid cell histiocytomas. The majority of cutaneous histiocytic lesions, including juvenile xanthogranuloma, Langerhans cell histiocytosis and Rosai-Dorfman disease, were positive for CD163.

CONCLUSION

CD163 is a useful adjunct in distinguishing AFX from other malignant cutaneous spindle cell tumors and offers improved specificity in identifying cutaneous histiocytic/dendritic lesions.

Cellular neurothekeoma with melanocytosis

Cellular neurothekeoma (CNT) is a benign dermal tumor mainly affecting the head and neck and the upper extremities. It is characterized histologically by interconnecting fascicles of plump spindle or epithelioid cells with ample cytoplasm infiltrating in the reticular dermis. The histogenesis of CNT has been controversial, although it is generally regarded as an immature counterpart of classic/myxoid neurothekeoma, a tumor with nerve sheath differentiation. Two rare cases of CNT containing melanin-laden cells were described. Immunohistochemical study with NKI/C3, vimentin, epithelial membrane antigen, smooth muscle antigen, CD34, factor XIIIa, collagen type IV, S100 protein and HMB-45 was performed. Both cases showed typical growth pattern of CNT with interconnecting fascicles of epithelioid cells infiltrating in collagenous stroma. One of the nodules contained areas exhibiting atypical cytological features. Melanin-laden epithelioid or dendritic cells were diffusely scattered throughout one nodule, and focally present in the peripheral portion of the other nodule. Both nodules were strongly immunoreactive to NKI/C3 and vimentin, but negative to all the other markers employed. CNT harboring melanin-laden cells may pose diagnostic problems because of their close resemblance to nevomelanocytic lesions and other dermal mesenchymal tumors. These peculiar cases may also provide further clues to the histogenesis of CNT.

Scar-like lesion on dorsal nose (cellular neurothekeoma)

Neurothekeomas are tumors of neural differentiation and of unknown origin that occur in females at the 2nd and 3rd decades of life. They usually affect the face with an unspecific clinical aspect. The histological features include cellular or mixoid differentiation and immunohistochemistry can be positive for protein s-100, vimentin and epithelilal membrane antigen (EMA). This case report presents a 13-year-old female patient with nasal neurothekeoma of cellular variety and strongly positive for vimentin and s-100; and negative for EMA.

An update on plexiform fibrohistiocytic tumor and addition of 66 new cases from the Armed Forces Institute of Pathology, in honor of Franz M. Enzinger, MD

The seminal article of Drs Franz Enzinger and Renyuan Zhang in 1988 defined plexiform fibrohistiocytic tumor (PFHT) as a distinctive entity. They described 65 cases (from 1965 to 1985) in children and young adults, with female and upper extremity predominance. These tumors were morphologically divided into 3 groups: fibroblastic, histiocytic (often with osteoclast-type giant cells), and mixed. Most tumors exhibited a plexiform and infiltrative arrangement of cells at the dermal/subcutaneous junction. Two fibroblastic PFHT had a metaplastic bone formation. Absence of cellular pleomorphism, low mitotic activity, dense hyalinization, hemorrhage, and chronic inflammation were observed. Vascular invasion was present in 1 recurrent, yet nonmetastatic, case. Tumors were negative for S100 protein, desmin, cytokeratin, factor VIIIrag, and lysozyme. Most patients were without disease up to 60 years after excision; 32 (37.5%) cases with follow-up recurred and 2 of those patients had regional lymph node metastasis at 9 and 36 months, respectively, yet there were no systemic metastases. In the interim, there have been additional studies on PFHT. We wanted to update the literature and add 66 new PFHT cases (1986-present) from the Armed Forces Institute of Pathology, since this seminal article, in honor of Dr Franz Enzinger. There were 37 men and 29 women; patient age ranged from 1 to 77 years (median, 20 years; 53% of patients were younger than 20 years). Twenty-eight cases occurred in the upper extremity (mostly forearm), 16 in lower extremity, 11 in trunk, 9 in head and neck, and 2 of unknown site. Although most cases were observed at the dermal/subcutaneous interface, 22 cases were predominantly dermal, and the rest predominantly subcutaneous, with 4 superficially involving skeletal muscle. Except for 12 predominantly dermal cases, most cases had an infiltrative growth pattern. Thirty-four cases were predominantly histiocytic, 16 predominantly fibroblastic, and the remaining 16 mixed. Two fibroblastic cases demonstrated the microfat cells (probably secondary to subcutis infiltration). All cases exhibited a plexiform growth pattern of small- to medium-sized nodules; 41 cases had giant cells, mainly osteoclast type, often the predominantly histiocytic type. The purely fibroblastic often had surrounding inflammation, 2 cases with marked inflammation. Perineural growth was observed in 5 cases, peri-Pacinian corpuscle growth in 2 cases, adnexal trapping in several, and, increased hyalinized collagen in 17 cases. Eight cases demonstrated focal myxoid change. Only 1 case, a histiocytic, had bone formation. Although increased cytologic atypia and mitotic activity were noted in a few cases, an atypical mitosis was only observed in 1 case. No cases demonstrated vascular or lymphatic invasion or necrosis. The tumors were generally positive for CD68 and SMA, occasionally for MSA, and negative for keratin, desmin, HMB45, S100 protein, and CD34. Overall, the findings were very similar to the original observations made by Dr Enzinger and his colleague, with the minor exceptions of roughly equal sex distribution (possibly due to timely referral bias), and additional morphologic features of myxoid change, adnexal sparing, increased inflammation, and microfat similar to recently described lipofibromatosis. The relationship between PFHT and cellular neurothekeoma is also explored.

Facial neurothekeoma in a 10-year-old child

Neurothekeoma is a rare and benign tumour that occurs most frequently on the head and neck. It is classified as a nerve sheath tumour and epidemiologically occurs in young adults. It is rare to find these tumours occurring in children. The following report describes a case of neurothekeoma in a young girl, its treatment and a review of the literature. Specific histological analysis may reveal atypical and aggressive features, which, in turn, affect resection and reconstructive options.

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=10 years of age and only 20% 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.

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.

Atypical cellular neurothekeoma treated with Mohs micrographic surgery

BACKGROUND

Atypical cellular neurothekeoma is a rare neoplasm generally regarded as a benign tumor with locally aggressive behavior. Recurrence is common with inadequate excision, but metastatic disease has yet to be reported.

OBJECTIVE

The objective was to report a case of atypical cellular neurothekeoma of the nasal ala in a young woman treated by Mohs micrographic surgery. The biologic behavior and histopathology will be reviewed.

METHODS

Case report and review of the literature.

RESULTS

The neoplasm was extirpated in a three-stage, five section Mohs surgery procedure. The resulting defect was repaired by a two-stage, pedicled nasolabial transposition flap with a cartilage graft taken from the ipsilateral ear. No clinical recurrence was noted after 6-months of follow-up.

CONCLUSION

Mohs micrographic surgery is unsurpassed in its efficacy in treating a wide variety of nonmelanoma skin cancers. Although most commonly used to address basal and squamous cell carcinoma, it has also been reported as a successful treatment for melanoma and a wide variety of cutaneous malignancies. We discuss a case of atypical cellular neurothekeoma removed with the Mohs technique. Debate in the literature is ongoing regarding the true histogenesis of this rare tumor. Because of this tumor's local destructive behavior and propensity to recur with inadequate resection, we recommend Moths micrographic surgery for the treatment of cellular neurothekeomas.

Mixed-Type Neurothekeoma Presenting with an Unusual Clinical Appearance of Multiple Satellite Lesions on the Back

BACKGROUND

Neurothekeoma is a rare cutaneous neoplasm, often occurring as a nondescript cutaneous nodule on the central face, shoulders, and upper extremities.

OBJECTIVE

To present a patient with mixed-type neurothekeoma with an unusual clinical presentation.

METHODS

We report a 29-year-old female who developed an asymptomatic, red, dermal nodule with satellite papules on the back over a period of 6 months.

RESULTS

The coalescing papules on the back were excised, and the histopathology and immunohistochemical study revealed a mixed-type neurothekeoma.

CONCLUSION

Neurothekeoma usually presents with a small, solitary, and slow-growing nodule or papule on the upper body. The case is interesting because of the unusual clinical manifestation of one dermal tumor with several satellite lesions.

Multiple cellular neurothekeomas - a case report and review on the role of immunohistochemistry as a histologic adjunct

BACKGROUND

Cellular neurothekeoma is a relatively rare, benign cutaneous neoplasm, which usually presents as a solitary papule or nodule involving the head and neck area of young adults. Multiple neurothekeomas have not, to date, been known to occur.

METHODS

We report a 30-year-old, otherwise healthy, male who presented with multiple neurothekeomas (15) in the head and neck area over a period of 12 years.

RESULTS

While the unifying feature of all biopsied (10 of 15) lesions was the presence of epithelioid cells--the lesions differed in their cellularity and the degree of sclerosis of the stromal component. Antigenic profiling of the lesional cells revealed expression of vimentin, NKI/C3, PGP 9.5, factor XIIIa and CD68 but not S100, HMB45, MelanA, EMA, MSA, desmin, CD57 or NGF-R.

CONCLUSIONS

This case report is the first to document the occurrence of multiple cellular neurothekeomas. An unusual histologic feature of some of the biopsied lesions was the presence of a markedly sclerotic stroma.

[Cellular neurothekoma in an 11-year-old child]

INTRODUCTION

Neurothekoma is a rare benign tumor which must be distinguished from certain malignant tumors such as fibrohistiocyte tumors or plexiform cell tumors, neurotropic melanomas and clear-cell sarcoma.

CASE REPORT

An 11-year-old girl consulted for a recurrent subcutaneous tumor of the chin which had been operated 4 months earlier. The resection was incomplete. A wider revision resection successfully stopped recurrence. The histology study established the diagnosis of neurothekoma due to the presence of mitosis atypia, cellular nodules, and extension to the hypodermis. Immunohistochemistry confirmed the diagnosis.

DISCUSSION

Neurothekoma is a benign tumor observed in young women, mainly on the face. It occurs as a dermal cohesive mass without infiltration of the epidermis. The typical immunohistochemical pattern enables differential diagnosis with myxoid neurothekoma, melanocytic and nervous system tumors. Surgical resection is indicated.

Nerve Sheath Myxoma

This report describes the clinicopathologic findings in 57 cases of nerve sheath myxoma. Our study group included 34 males and 23 females, ranging from 8 to 72 years of age at the time of their first surgical procedure (mean, 36 years; median, 34 years). The patients typically presented with solitary, superficial, multinodular masses in the 0.5- to 2.5-cm size range. Eighty-six percent of cases occurred in the extremities, with the most common locations being the hand/fingers (n = 22), knee/pretibial region (n = 10), and ankle/foot (n = 7). Only 7 cases (12.3%) involved the trunk or head and neck region. The tumors were generally slow growing, and often, they were present for many years before surgical resection was sought. In the majority of instances, the lesions were painless. Histologically, the tumors involved the dermis and/or subcutis, and they formed distinct multinodular/multilobular masses with abundant myxoid matrix and a peripheral fibrous border. All cases had small epithelioid Schwann cells in corded, nested, and/or syncytial-like aggregates, a variable number of Schwann cells with a ring-like appearance, and scattered spindled and stellate-shaped Schwann cells. These cells often had cytoplasmic-nuclear invaginations, and they were immunoreactive for S-100 protein, glial fibrillary acidic protein, neuron specific enolase, and CD57. They were also bordered by collagen IV. Epithelial membrane antigen-positive perineurial cells were typically present in small numbers, primarily in the fibrous tissue directly adjacent to the myxoid nodules. CD34-positive intraneural fibroblasts were generally sparse. Mitotic figures were uncommon. All cases were initially managed by simple excision, and in almost all instances, tumor extended to the tissue edge. Follow-up information is available for 34 patients (follow-up range, 8 months to 28 years; median follow-up interval, 14 years 3 months). Sixteen patients (47%) had one (n = 11) or more (n = 5) local recurrence of their tumor, and 2 additional patients had findings suspicious for a recurrence. Nerve sheath myxomas are morphologically distinct peripheral nerve sheath tumors with a peak incidence in the fourth decade of life and a strong predilection for the extremities. These tumors have a relatively high local recurrence rate when managed by simple local excision. They appear to be unrelated to so-called cellular and mixed-type neurothekeomas.

Cellular neurothekeoma with histiocytic differentiation

BACKGROUND

It is generally accepted that the two types of neurothekeoma (myxoid type and cellular type) represent the two poles of a spectrum. This concept, however, has recently been challenged, and cellular neurothekeomas have been suggested as a separate classification and are included in the "fibrohistiocytic" category by some authors. Cellular neurothekeomas have been reported to show negative immunohistochemical staining for histiocytic markers, and PG-M1 is now considered to be the most reliable histiocytic marker.

CASE REPORT

We report a case of cellular neurothekeoma. The histopathological features in this case were typical for cellular neurothekeoma. Immunohistochemically, the neoplastic cells were diffusely positive for S-100A6 protein, PGP9.5, CD10, CD68 (KP1), PG-M1, and Vimentin, and negative for other antibodies including S-100 protein and factor XIIIa.

CONCLUSIONS

Cellular neurothekeoma expressing both KP-1 and PG-M1 is considered to show histiocytic differentiation, and may be interpreted as a neoplasm with immature nerve sheath differentiation, incidentally expressing histiocytic markers, or as an undifferentiated neoplasm derived from the neural crest cells of nerve sheath/fibrohistiocyte lineage. These results, such as the concomitant expressions of PGP9.5/S-100A6 and PG-M1/CD68 (KP-1), support the theory of multiple differentiation in cellular neurothekeomas. The significance of the expression of CD10 in this cellular neurothekeoma is unclear.

Microphthalmia transcription factor and NKI/C3 expression in cellular neurothekeoma

While the usual or myxoid-type neurothekeoma has been reasonably well established as being a tumor of neural origin, the cellular neurothekeoma remains in disputed histogenesis. We studied a series of 11 cellular neurothekeomas using paraffin immunoperoxidase staining with microphthalmia transcription factor (Mitf), NKI/C3, and S-100. The majority of the tumors in our series stained with NKI/C3 (9/11) and Mitf (9/11). All failed to stain with S-100. Furthermore, we divided our series of cellular neurothekeomas according to cytomorphology; tumors demonstrating predominantly spindled morphology, predominantly epithelioid morphology, and mixed spindle and epithelioid morphology. The two tumors that failed to stain with NKI/C3 both demonstrated predominantly spindled morphology. One of the tumors that failed to stain with Mitf showed exclusive spindled morphology, while the other showed mixed morphology (spindle and epithelioid). Two of the tumors, which stained strongly with Mitf, however, showed exclusive epithelioid morphology. This current study furthers the concept that cellular neurothekeoma is a tumor of neuroectodermal origin, and further suggests that it may express some component of melanocytic differentiation.

Antibody to S100a6 protein is a sensitive immunohistochemical marker for neurothekeoma

BACKGROUND

Neurothekeoma is a benign tumor of putative peripheral nerve sheath origin. It occurs in a myxoid (classic) variant, cellular variant, and intermediate (mixed) variant. Cellular neurothekeoma (CNT) usually involves the head and neck or extremities of young patients. Histologically, CNT can be confused with melanocytic and fibrohistiocytic lesions. An immunohistochemical antibody panel is often necessary to confirm the histological impression and exclude melanocytic and/or fibrohistiocytic lesions.

METHODS

Formalin-fixed, paraffin-embedded archival tissues were evaluated by immunohistochemistry using antibodies specific for S100A6 and PGP9.5 in 11 cases of neurothekeoma (seven cellular, four myxoid). A variety of other antibodies were evaluated by immunohistochemistry at the time of initial diagnosis.

RESULTS

All 11 neurothekeoma cases were positive for S100A6 protein (four cases, weak/1+; seven cases, strong/2+), corresponding to 100% sensitivity. In contrast, eight of 11 neurothekeoma cases (73% sensitivity) were positive for PGP9.5. All seven CNT cases were negative for S100B, as expected.

CONCLUSIONS

Anti-S100A6 is a highly sensitive antibody for neurothekeomas, including CNT, and, in our experience, is superior in sensitivity to PGP9.5. However, like other antibodies used in evaluating neurothekeomas, S100A6 lacks specificity, as has been demonstrated in previous studies. Nevertheless, S100A6 can be useful in an immunohistochemical antibody panel to evaluate lesions where the differential diagnosis includes CNT.

CD99 immunoreactivity in atypical fibroxanthoma: a common feature of diagnostic value

Atypical fibroxanthoma (AFX), a pleomorphic superficial cutaneous tumor of low-grade malignancy, shares many morphologic features with malignant melanoma (MM) and squamous cell carcinoma (SCC). Absence of S-100, keratin, and desmin immunoreactivity is the clue for this diagnosis. In a search for positive markers, we tested 26 cases of AFX with 2 antibodies: O13 (CD99) and protein gene product 9.5 (PGP9.5). We also included 10 cases of poorly differentiated SCC and 10 cases of MM in the study. In AFX, CD99 immunoreactivity was present in 19 cases (73%), whereas focal PGP9.5 immunoreactivity was found in only 9 cases (35%). None of the SCC cases showed CD99 immunostaining. No CD99 immunoreactivity was found in 9 of 10 cases of MM. To our knowledge, this is the first report of CD99 and PGP9.5 immunostaining in AFX. We believe, based on our results, that CD99 may be a helpful "positive" feature in the histopathologic diagnosis of AFX.

Cellular neurothekeoma of the oral mucosa

Cellular neurothekeoma is an unusual benign neoplasm which, despite its name, is of uncertain origin. This report describes a cellular neurothekeoma of the cheek mucosa, the first at this site. The tumour presented in a 29-year-old man as a discrete mucosal thickening. Histology showed a generally well circumscribed, but unencapsulated, solid tumour which replaced the entire lamina propria and permeated between minor salivary glands and bundles of striated muscle in the submucosa. There was a sub-epithelial Grenz zone. The tumour was composed of nodules of pale, epithelioid cells separated by fascicles of spindle cells, with smaller strands and nests superficially. The nuclei were vesicular and, though mainly bland, occasionally atypical. The stroma was moderately infiltrated by mixed chronic inflammatory cells. Prominent nerves and blood vessels were seen at the periphery of the lesion, and neoplastic cells were noted within intact striated muscle fascicles. With immunohistochemistry, all the neoplastic cells strongly expressed NKI/C3, synaptophysin, neurone-specific enolase and vimentin, some expressed smooth muscle actin and PGP 9.5, but all were negative for S100, factor XIIIa, CD34, CD56, CD57, CD68, chromogranin A, desmin, epithelial membrane antigen and von Willebrand factor. The origin of the lesion is thus speculative. It was, however, completely excised and in 12 months there has been no recurrence.

Combined dermatofibroma: co-existence of two or more variant patterns in a single lesion

AIMS

Based on a series of 25 cases, we define and characterize combined dermatofibroma, a tumour comprising two or more variant patterns of dermatofibroma in a single lesion.

METHOD AND RESULTS

Dermatofibroma may present with a wide variety of architectural, cellular or stromal peculiarities. Architectural peculiarities include deep penetration, atrophy, collarette formation, fascicular to plexiform architecture, massive haemorrhage, prominent haemangiopericytoma-like vascularity and palisading; cellular peculiarities the presence of epithelioid cells, clear cells, granular cells, prominent myofibroblastic differentiation and atypical giant cells ('monster cells'); or stromal peculiarities such as prominent sclerosis, mucin, haemosiderin and cholesterotic deposits. In combined dermatofibromas two or more of these features are seen in complex or inhomogenous combination such as the silhouette of a deep penetrating dermatofibroma with an 'ordinary' storiform pattern in the upper and granular cell differentiation in the lower part of the lesion; or a dermatofibroma with ordinary features in the upper, prominent sclerosis in the middle and clear cells in the lower portion of the lesion; or the characteristic epidermal collarette and cells of epithelial cell histiocytoma with a plexiform ('neurothekeoma-like') architecture surrounded by a myxoid stroma with spindle-shaped to stellate cells. Clinically, these lesions preferentially occur on the lower extremities of young to middle-aged females, frequently with the diagnosis of a fibrohistiocytic lesion. Apart from one recurrence follow-up was uneventful in all other cases. Immunohistochemically, lesions are consistently positive with KiM1p, variably positive for factor XIIIa, smooth muscle specific actin and with KP1 (CD68), NK1C3 and E9.

CONCLUSION

Recognition of combined dermatofibroma allows the histopathologist to apply a confident benign label to unusual lesions which might otherwise elude diagnosis, or tempt description of 'new' entities and to avoid a misdiagnosis of malignancy.

Problematic pigmented lesions: approach to diagnosis

A number of pigmented lesions are difficult to classify and raise the possibility of a melanoma diagnosis. Care should be exercised to exclude non-melanocytic lesions, and benign melanocytic entities, both of which can mimic melanoma histologically. In addition, the possibility of the lesion being a melanoma variant or epidermotropic metastasis should be considered. There will still be some cases that are difficult to resolve. These usually fall into one of three categories: atypical junctional melanocytic lesion versus early melanoma; naevus versus naevoid melanoma; and atypical Spitz, cellular blue, and deep penetrating naevi versus thick melanoma. These will pose problems even for experts. The atypical Spitz lesions are perhaps the most important category because they tend to be from younger individuals, the differential diagnosis is thick melanoma, and there is no single discriminating histological feature.

Myxoma is not a single entity: a review of the concept of myxoma

Myxoid lesions can be subdivided into (1) mainstream myxomas of soft tissues, (2) mainstream myxomas located outside the soft tissue, (3) inadequately substantiated myxomas, (4) myxoid soft tissue tumors or lesions not regarded as myxomas, (5) myxoid fatty conditions, (6) other soft tissue lesions and tumors that are sometimes markedly myxoid, (7) other soft tissue tumors in which myxoid foci may be seen, and (8) nonneoplastic myxoid conditions of soft tissue. More than 60 such conditions are listed and the five entities regarded as mainstream soft tissue myxomas (namely, intramuscular myxoma, juxta-articular myxoma, superficial angiomyxoma, aggressive angiomyxoma, and myxoid neurothekeoma [myxoma of nerve sheath]) are reviewed in detail. Intramuscular myxoma is exclusively intramuscular, usually affects middle-aged women, is most commonly located in the thigh, and does not recur after simple excision. Multiple intramuscular myxomas are rare and are usually associated with monostotic or polyostotic fibrous dysplasia and Albright's syndrome. Juxta-articular myxoma histologically resembles an intramuscular myxoma, but involves periarticular tendons, ligaments, joint capsules, muscles, and even the subcutis of adults. It may be associated with osteoarthritis of the adjacent joint. Some 30% recur locally. Superficial angiomyxoma also has been called cutaneous myxoma. It affects all ages, with a peak incidence in the third and fourth decades; arises in the trunk, lower limb, head, and neck regions; and usually measures less than 5 cm in diameter. Epithelial components are present in approximately 25% of tumors. Approximately one third recur locally, but there have been no metastases. Patients with multiple lesions may have the Carney complex. Aggressive angiomyxoma usually arises in the pelvic and perineal regions and affects females seven times as often as males. Tumors usually measure 10 cm or more in diameter, invade surrounding tissues, and recur in approximately 50% of cases. None have metastasized. Myxoma of nerve sheath (the myxoid variant of neurothekeoma) preferentially affects the dermis and subcutis of the cervicofacial areas and shoulders of young women. Most patients are younger than 40 years; one third of them are in the second decade of life. The majority of tumors measure between 0.5 and 1.5 cm. Only three of 102 cases compiled from the two largest published series recurred; none metastasized. The different clinicopathologic features and behavior of these five mainstream myxomas indicate that myxoma is not a single entity.