Malignant epithelioid schwannoma of superficial soft tissue? A case report with immunohistology and electron microscopy

Cutaneous epithelioid malignant peripheral nerve sheath tumour: a clinicopathological analysis of 11 cases

AIMS

Epithelioid malignant peripheral nerve sheath tumour (E-MPNST) is a distinctive variant of malignant peripheral nerve sheath tumour characterized by the predominance of epithelioid cells, diffuse S100 positivity and infrequent association with neurofibromatosis type 1. The aim of this study was to further delineate clinicopathological features of cutaneous E-MPNST, correlate them with disease outcome and discuss differential diagnosis.

METHODS AND RESULTS

We analysed 11 cutaneous E-MPNSTs (six males, five females, median age 49 years, median size 1.6 cm). Tumours showed a predilection for lower extremities (45%) and trunk (45%), followed by upper extremity (9%). Follow-up was available for nine of 11 patients (range 24-100 months, median 52 months). Four patients had an uneventful clinical course (44%), two developed local recurrence(s) (22%) and three died due to disseminated disease (33%). No histological parameters were found to predict local recurrence(s), development of distant metastases or disease outcome, including size, percentage of epithelioid component, number of mitoses per 10 high-power fields, degree of nuclear atypia or site of occurrence (dermis, dermis/subcutis, subcutis) (P > 0.05). Immunohistochemically, all tumours were diffusely S100-positive, with a subset displaying loss of integrase interactor 1 (INI1) expression (50%).

CONCLUSIONS

Cutaneous E-MPNST has the potential to pursue an aggressive clinical course, associated with wide dissemination and unfavourable disease outcome.

Epithelioid malignant peripheral nerve sheath tumour in a dog

An unusual morphological variant of malignant peripheral nerve sheath tumour, in which the cells exhibited a predominantly epithelial morphology, was diagnosed in a dog. The animal had a history of progressive ataxia. Post-mortem examination revealed an infiltrative growth in the sublumbar region, encroaching on the L1 and L2 vertebral bodies; additional masses were observed in the kidneys, liver and lungs. Histologically, the subcutaneous mass was composed of a dense population of spindle-shaped cells arranged in fascicles. The internal masses were composed of epithelioid cells arranged in a nodular pattern. Immunohistochemically, the spindle-shaped cells of the subcutaneous mass were positive for S-100, and the epithelioid cells of the internal growths exhibited weak S-100 immunoreactivity.

Superficial malignant schwannoma of the scalp

BACKGROUND

Malignant schwannoma is a rare sarcoma that is located mostly on trunk and extremities; the head and neck are unusual sites for its development. Almost half of these tumors arise from neurofibromas with or without von Recklinghousen's disease, and most of the remainder develop de novo from peripheral nerve trunks. Development in the superficial soft tissues is extremely rare.

OBJECTIVE

To present a case of superficial malignant schwannoma of the scalp, which is an uncommon presentation.

METHODS

An 80-year-old male patient presented with a painless ulceration on his scalp. The clinical and radiologic properties of the tumor were consistent with a skin tumor.

RESULTS

The lesion was excised, and reconstruction was achieved by transposition scalp flap. Malignant schwannoma was given as diagnosis by histopathologic examination with immunohistochemistry.

CONCLUSION

Malignant schwannomas may also occur in the skin. Clinically, these superficial forms closely resemble skin tumors, especially malignant melanoma. The treatment of choice in these tumors is wide resection combined with radiotherapy.

Subcutaneous malignant epithelioid schwannoma with cartilaginous differentiation

BACKGROUND

Malignant epithelioid schwannoma is a rare tumor. The aim of this study is to describe a case of subcutaneous malignant epithelioid schwannoma with cartilaginous differentiation.

METHODS

Histological, immunohistochemical, and ultrastructural examinations were performed on a tumor that arose on the back of a 37-year-old woman.

RESULTS

Histologically, the tumor predominantly consisted of small, round or polygonal cells arranged in cords or nests. Immunohistochemical study revealed that the tumors cells were positive for vimentin, S-100 protein, glial fibrillary acidic protein and neuron specific enolase. The cells were negative for HMB-45, keratin, epithelial membrane antigen, and CAM5.2. Electron microscopic study showed closely associated cells with undifferentiated features. The cells were devoid of external laminae and cellular junctions.

CONCLUSION

Malignant epithelioid schwannoma should be pathologically differentiated from other epithelioid tumors with cartilaginous elements.

Malignant peripheral nerve sheath tumor of the skin: a superficial form of this tumor

A case of malignant peripheral nerve sheath tumor (MPNST) of the skin, which is a superficial form of this type of tumor, is described. Although our patient did not present the usual diagnostic criteria for MPNST, the clinicopathologic findings for both the initial and recurrent tumors were compatible with those of the ordinary type of this tumor and not with those of neurotropic melanoma or cellular schwannoma. The recurrent tumor presented progression compared to the low grade malignancy in the original tumor. Perhaps because of the superficial location of the tumor our patient showed an unexpected favorable outcome in spite of repeated recurrences. Reports indicate that, of the superficial forms, the ordinary type is still less frequently encountered than the epithelioid type. We also discuss the differentiation between MPNST of the skin and neurotropic melanoma.

Desmoplastic neurotropic melanoma. A clinicopathologic analysis of 28 cases

BACKGROUND

Desmoplastic neurotropic melanoma (DNM) is a rare variant of malignant melanoma, the natural history and histogenesis of which still are being defined.

METHODS

The clinical and histologic features of 28 cases of DNM were studied. All published cases of DNM to date were reviewed. Paraffin sections from 26 cases were investigated with a panel of 10 tissue markers. The ultrastructural features of seven cases were evaluated.

RESULTS

A comparison of this study's findings with that of other published cases revealed many similarities regarding clinical and pathologic findings and outcome. The patients were white (15 men:13 women; mean and median age, 59 years; range, 22-83 years). Most tumors were located on the head and neck (75%) and were nonpigmented (57%). An associated intraepidermal melanocytic proliferation was identified in 85% of the patients (lentigo maligna in 56%). Histologically, the dermal tumors were composed of tapered, nonpigmented spindle cells in peripheral nerve sheath patterns resembling neuromas, schwannomas, neurofibromas, and perineurial proliferations accompanied by variable neurotropism and desmoplasia; desmoplasia was the most notable feature in most tumors. The mean depth of tumor invasion was 4.1 mm (range, 0.32-9.0 mm). Tumors with continuity between the epidermal and dermal components had a significantly thinner depth of invasion and a more extensive intraepidermal melanocytic proliferation than those tumors with a grenz zone between the two components (2.3 mm vs. 4.6 mm, P = 0.015). Mitotic activity ranged from 0/HPF in 10 cases, 1-6/high power field (HPF) in 12 cases, and to greater than 6/HPF in 4 cases. An ulcer was present in 5/27 tumors, regression in 4/27, a microsatellite in 1, and brisk and had nonbrisk tumor infiltrating lymphocytic responses in 2 and 14, respectively. Vimentin was uniformly positive and keratins AE1.3 and Cam 5.2 and Leu-7 were uniformly negative. S100 protein, also uniformly positive, had patchy reactivity in most tumors that expressed EMA (43%). Smooth muscle actin (52%), neuron-specific enolase (42%), and FXIIIa (30%) had patchy positivity. HMB-45 was reactive only in the epidermal and superficial papillary dermal component in 21% of cases. Ultrastructurally, the common features were long, often intertwining cellular processes, intercellular junctions, and discontinuous basal lamina. Melanosomes were not identified. Follow-up data available on 26/28 patients (mean, 36 months; median, 24 months; range, 5-132 months) showed 20 (70%) alive without disease, 2 alive with disease and 3 dead from disease. Seven patients had recurrent local tumor (multiple in four); four had lymph node metastases, and three had visceral metastases. Patients with recurrent disease of any type had significantly thicker tumors (5.4 mm vs. 3.4 mm, P = 0.046) and were more likely to have an ulcerated tumor (P = 0.03). Actuarial 5-year survival for tumors with greater than a 4-mm thickness was 72%, which was greater than that for other types of melanoma with greater than a 4-mm thickness.

CONCLUSIONS

Desmoplastic neurotropic melanomas are neuroectodermal tumors that usually arise from an intraepidermal melanocytic proliferation but rarely develop de novo in the dermis. Schwannian and perineurial differentiation may account for the desmoplasia and neurotropism encountered in these neoplasms. Desmoplastic neurotropic melanomas present at a more advanced stage locally and may be associated with a better survival than associated with conventional melanomas of similar depth of invasion.

Superficial epithelioid schwannoma presenting as a subcutaneous upper eyelid mass

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Malignant sinonasal epithelioid schwannoma

Malignant schwannomas are rare neoplasms that are seldom found in the head and neck. Few cases have been reported involving paranasal sinuses and none of them was of the "epithelioid" type. In this report, an unusual case of epithelioid malignant schwannoma involving the maxillary sinus, nasal cavity and orbit is presented. The patient was a 27-year-old male with a history of headache, nasal obstruction and epistaxis. Histologically, the tumour had a biphasic pattern with spindle and epithelioid elements which led to a differential diagnosis with malignant melanoma. It had also to be distinguished from other neoplasms, such as squamous cell carcinoma and olfactory neuroblastoma because of it location. Immunohistochemical positivity for S-100 protein, glial fibrillary acidic protein and vimentin together with negativity for HMB-45 and cytokeratins, as well as mesaxon formation detected with electron microscopy were conclusive in the diagnosis. The patient was treated with surgical excision and radiotherapy but local recurrence and metastases occurred, and he died within 1 year after initial diagnosis.

Cutaneous malignant peripheral nerve sheath tumour (MPNST) of the hand: a review of current literature

Malignant peripheral nerve sheath tumours (MPNST) are spindle cell sarcomas normally situated in the deep soft tissues. Cutaneous MPNST is an uncommon variant, usually occurring in the head and neck. When it arises in the upper limb this tumour may pose a considerable diagnostic and therapeutic problem. We present a case of cutaneous MPNST arising in the hand. Tumour extension was exclusively perineural along three major nerve trunks from an interdigital origin. Current knowledge of the clinical behaviour of cutaneous MPNST is reviewed.

The fibroma-like variant of epithelioid sarcoma

Five cases of a previously undescribed variant of epithelioid sarcoma are presented. This variant differs from the usual lesion in its absence of the typical necrobiotic nodular epithelioid pattern. It is instead composed of deceptively bland fibrohistiocytic and myoid cells arranged in a fibroma-like or dermatofibroma-like pattern with an affinity for osseous involvement. The clinical presentation, ultrastructural features, and presence of vimentin and low molecular weight keratin within the tumor cells justifies their designation as an epithelioid sarcoma variant.

Neurofibrosarcoma of skin and subcutaneous tissues

In this report, we describe 13 cases of primary neurofibrosarcoma of the skin. The tumor presumably arises from small cutaneous nerves, is locally aggressive, and has a potential for metastasis. Characteristic histopathologic features include proliferating atypical spindle cells with slender wavy and pointed nuclei; hypocellular areas with loose, myxoid stroma; and areas of organoid organization such as palisading, whorly, storiform, and tactile body-like formations. The S-100 stain is positive in about 60% of cases. In the current series, most tumors arose in deep dermis and were grade 2 malignant lesions with a moderate degree of cytologic atypia and 2 or fewer mitoses in 10 high-power fields. Three patients died of their malignant lesion. Only two tumors metastasized. Of the 10 patients who had local recurrence, 5 had multiple recurrent lesions. Neurofibrosarcoma should be considered in the differential diagnosis of malignant tumors of the skin. A complete surgical resection of the primary tumor with adequate margins of surrounding normal-appearing tissue is advised.

Malignant schwannoma. A case report and review of the literature

A rare case of a malignant schwannoma presenting as a central fracture-dislocation of the acetabulum is reported. Histological examination showed a high-grade sarcoma. A pleural metastasis was present. A local reconstructive procedure consisting of local tumor excision with an acetabular prosthetic replacement and adjunctive radiation therapy was elected for the patient, who had a short-term prognosis.

Expression of glial filament protein (GFP) in nerve sheaths and non-neural cells re-examined using monoclonal antibodies, with special emphasis on the co-expression of GFP and cytokeratins in epithelial cells of human salivary gland and pleomorphic adenomas

We describe two novel monoclonal antibodies specific for glial filament protein (GFP), i.e., GF12.23 and GF12.24 (both IgG2a]. These cross-react over a broad range of species with epitopes located in the alpha-helical rod domain typical of all intermediate filament (IF) proteins. These monoclonal antibodies were used, in conjunction with other monoclonal GFP antibodies, rabbit antiserum to GFP, and various antibodies to other cytoskeletal proteins, to examine the occurrence of GFP in cells outside of the central nervous system of rodents, cows, and humans. We detected some scattered GFP-containing cells in the neural sheaths in some species but not in others, and we obtained different results when comparing the rabbit antisera with the monoclonal GFP antibodies. In the enteric glia of rats, we observed GFP-positive cells with all of the antibodies used, whereas in human intestine, the various monoclonal antibodies showed no reaction with any intestinal cells. Similarly, no GFP was detected in surface cells of the lens of cows and rats using any of the GFP antibodies, whereas some reaction was seen in murine lens tissue. We were also unable to detect GFP-positive cells in human, bovine, or rat liver with any of the monoclonal antibodies, which is in contrast to the reactivity of the rabbit GFP antisera with some stellate perisinusoidal cells of rat but not bovine or human liver. The possible reasons for the discrepancies between the different species and the different antibody preparations used are discussed. In addition, using double-label immunofluorescence microscopy, we showed that normal human parotid glands contain a certain type of epithelial cell that co-expresses cytokeratins and desmosomal proteins with GFP. The histological distribution of these GFP-positive cells suggests that they represent a subset of the myoepithelial cells present in this tissue. Cells co-expressing cytokeratins and GFP - in some cases, apparently together with vimentin as the third IF protein present - were also identified in tumors derived from this salivary-gland epithelium, i.e., pleomorphic adenomas, in which GFP-positive cells were relatively frequent in the myxoid and chondroid components, thus confirming the work of other investigators. Possible implications for the concept of histogenesis of these tumor cells are discussed, as are possible mechanisms resulting in the co-expression of IF proteins.

Epithelioid neurilemmoma of the trigeminal nerve: an immunohistochemical and ultrastructural study

A 50-year-old male presented with facial pain due to an extrinsic intracranial tumour involving pontine nerve roots. Biopsy and subsequent partial surgical excision indicated origin from the trigeminal nerve. Histologically the tumour had features of a neurilemmoma but in addition contained a population of epithelioid cells. Immunohistochemical studies demonstrated S100 protein in the non-epithelioid component but no reaction in the epithelioid cells, whilst vimentin was present in both cell types. Ultrastructurally the epithelioid cells showed features consistent with a Schwann cell nature and may represent a less well differentiated cell population derived from a Schwann cell precursor. The significance of these findings in relation to the cell of origin of neurilemmomas is discussed.