Cellular neurothekeoma with histiocytic differentiation

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.

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.

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.

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.

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.

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 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.

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.