Epithelioid Schwannoma Research Articles

Primary Mesenchymal Tumors of the Urinary Bladder: A Histological and Immunohistochemical Study of 30 Cases

The light microscopic and immunohistochemical features of 30 primary mesenchymal neoplasms of the urinary bladder are reported. Half of the cases represented smooth and striated muscle tumors (five leiomyomas, seven leiomyosarcomas including epithelioid and myxoid subtypes, one rhabdomyoma, one embryonal rhabdomyosarcoma and one alveolar rhabdomyosarcoma). One third of the tumors were of fibrohistiocytic origin (one fibrous histiocytoma and eight malignant fibrous histiocytomas including fascicular and storiform, inflammatory and pleomorphic subtypes). In addition, a malignant epithelioid schwannoma, a round cell liposarcoma, two hemangiomas and two mixed mesodermal tumors were observed. The morphology of the vesical mesenchymal tumors was identical to that of their counterparts known to occur in other sites, particularly in the soft tissue. Muscle-specific actin, alpha-1-antichymotrypsin, S-100-protein and neuron-specific enolase proved to be useful and reliable immunomarkers for differential diagnosis of poorly differentiated leio- and rhabdomyosarcomas, malignant fibrous histiocytomas and malignant schwannomas. Since some tumors coexpressed several classes of intermediate filaments, diagnostic immunocytochemistry should only be used considering a larger panel of antibodies and in close correlation with the histological and cytological features of the neoplasms.

Malignant cutaneous tumors in children: Twenty years of experience at a large pediatric hospital

The frequency of different malignant cutaneous tumors (MCTs), primary and metastatic, in children is not known. We reviewed all MCTs, primary and metastatic, seen during a 20-year period in a large general pediatric hospital. Fifty-three MCTs, 36 primary and 17 metastatic, were diagnosed in 36,207 pediatric dermatology patients. The incidence was 1.4 per 1000 patients. The relative frequency of occurrence of the different tumors was as follows: rhabdomyosarcoma, 25%; lymphomas, 19%; basal cell carcinoma, 13%; leukemia, 13%; neuroblastoma, 10%; malignant melanoma, 6%; squamous cell carcinoma, 6%; unclassified sarcomas, 4%; epithelioid schwannoma, 2%; ependymoma, 2%. The mean follow-up was 3 years; 48% died, 27% were lost to follow-up, and 25% are under control. We conclude that primary and metastatic MCTs in children are rare. Their types differ from MCTs in an older age population. MCTs in children are associated with a high mortality rate, often related to late recognition.

Malignant Epithelioid Schwannoma of the Skin Showing Partial HMB-45 Positivity

A malignant epithelioid schwannoma occurred on the right second toe of a 30-year-old Japanese man. It was a firm, flesh-colored, benign-appearing nodule and measured 13 x 9 mm in diameter and 6 mm in height. To our knowledge, this is the first case of malignant epithelioid schwannoma occurring on the toe. Histopathology was characterized by a circumscribed nodule in the dermis that predominantly consisted of atypical large epithelioid cells with some spindle cells whose proliferation was similar to that of the Verocay bodies seen in ordinary schwannoma. Fontana-Masson staining demonstrated no melanin pigment in the tumor at the light microscopic level. The eosinophilic cytoplasm contained abundant glycogen and was positive for S-100 protein and HMB-45, as usually seen in melanomas. Electron microscopy revealed that there was an abundance of long-spacing collagen in the extracellular matrix, and the cells contained numerous dense-cored granules. But no definite melanosomes were observed in any stage. As far as we are aware, this is the first case of a malignant epithelioid schwannoma showing HMB-45 positivity.

Malignant Primitive Neuroectodermal Tumor Presenting as a Scalp Nodule

We report a case of a 20-year-old woman who presented with a 3-year history of a stable cystic nodule on the scalp. Light microscopy of the excised nodule demonstrated a malignant small round cell undifferentiated neoplasm. Immunohistochemical studies suggested a neural crest origin, while ultrastructural examination revealed characteristics of schwannian differentiation. Both of these special techniques were essential in establishing the diagnosis of a malignant epithelioid schwannoma of superficial tissue (neurotropic melanoma, desmoplastic melanoma). We discuss the differential diagnoses and describe the immunohistochemical and ultrastructural characteristics of this tumor. This case illustrates the difficulty of diagnosing this rare malignant tumor, which masqueraded as a benign-appearing scalp lesion.

Augmentation of Human Cytotoxic T Lymphocytes against Autologous Tumor by a Factor Released from Human Monocytic Leukemia Cell Line

A human acute monocytic leukemia cell line, THP‐1, releases a factor which activates human cytotoxic (killer) T lymphocytes (CTL) against autologous tumor in vitro. The factor, named cytotoxic (killer) T cell activating factor (KAF), is an acidic protein of 70,000 to 100,000 dalton molecular size. Peripheral blood leukocytes from two patients, bearing epithelioid sarcoma or malignant schwannoma, were cultured for 7 days with individual autologous tumor to induce CTL directed to the corresponding tumor. Monocyte‐depleted peripheral leukocytes generated lesser CTL activity than the monocyte‐containing leukocyte population. However, the KAF was able to replace the monocyte function. The KAF acted at the CTL generation phase as well as the effector phase. The KAF‐activated killer cells possessed CD4‐8+ surface phenotype. The CTL killed autologous tumor or other unrelated tumor cell lines only when they shared some of the HLA class I antigens. It was also demonstrated that the KAF does not activate killer cells without proper antigenic stimuli, because the KAF‐augmented CTL possess specificity against autologous tumor or other HLA‐A or ‐B matched tumor cell lines. The therapeutic applicability of human KAF for anti‐tumor CTL therapy against autologous tumor is discussed.

Superficial malignant schwannoma on the face: A case for early radical surgery

A case of superficial epithelioid schwannoma is presented. The lesion arose as a skin papule in the infra-orbital region and recurring repeatedly over a five-year period, caused significant local morbidity without metastasis. Radical surgery was delayed in the hope of preserving binocular vision. The similarity of this tumour with a rare variant of malignant melanoma, the neurotropic melanoma, is discussed.

Malignant peripheral nerve-sheath tumors (malignant schwannomas). An immunohistochemical study of 29 cases.

Twenty-nine cases of malignant schwannoma consisted of three groups; 11 tumors associated with von Recklinghausen's disease (group I), nine tumors arising grossly from nerve trunks (group II), and 11 tumors so diagnosed basically on the histologic features (group III). Using the immunoperoxidase methods, the tumors were investigated with regard to S-100 protein, keratin, and epithelial membrane antigen (EMA). Approximately one-third of the cases (10 of 29) were devoid of S-100 positive cells and the remaining two-thirds (19 of 29) contained positive cells, with variable frequencies. The number of S-100 positive cells differed, depending largely on the presence or absence of neurofibroma-like areas in the tumor. The positive cells were rarely found in the group III tumors, which were neither associated with von Recklinghausen's disease nor connected to nerve trunks, even when their histologic features were unequivocal. Certain specific organoid structures in the tumor, such as neuroid or tactoid ones, were positive for S-100 protein. In one of the two malignant epithelioid schwannomas, the tumor cells were strongly positive for S-100 protein, thereby suggesting melanocytic differentiation. This tumor was interpreted as a melanocytic malignant schwannoma rather than a malignant melanoma, based in part on the fact that the overlying epidermis was uninvolved in this patient with von Recklinghausen's disease. True epithelial differentiation in one case of glandular schwannoma was verified by the positive stain of EMA along the inner surface of the glandular element.

Malignant Peripheral Nerve Tumors: A Clinicopathological and Flectron Microscopic Study

Sixteen cases of malignant peripheral nerve tumors that were recorded in the files of the Department of Orthopedics, National Cancer Center Hospital, Tokyo, between 1972-July 1983 were studied clinicopathologically. The patients' ages ranged from 24-51 years, and both sexes were affected equally. Histologically, in 13 cases of nerve sheath tumors the tumors were spindle-cell type, two of these patients had manifestation of multiple neurofibromatosis (von Recklinghausen's disease). One malignant epithelioid schwannoma was found to arise from the tibial nerve. Other two cases were of primitive neuroectodermal tumors (primary malignant peripheral neuroblastoma) which showed rosette formation. The common primary symptoms in all patients were a noticeable mass which increased in size over a variable period of time, with or without associated pain and tenderness. Ultrastructural findings of spindle-cell type (in 7 tumors examined) and epithelioid type (1 tumor) showed evidence of Schwann cell differentiation of the tumors in all cases. Immunohistochemically, by the PAP method (Sternberger), staining for S-100 protein was positive in 3 of 14 tumors. Ultrastructural findings in two S-100 protein-positive cases showed evidence of Schwann cell differentiation better than the S-100 protein-negative cases, such as pronounced interdigitation of cytoplasmic processes, presence of fibrous long-spacing collagen and well-developed basal lamina. Local recurrence occurred in nine patients, and metastasis was found in five. The total 5-year survival rate was 58.5%. Tumors associated with multiple neurofibromatosis and primary peripheral neuroblastomas had the worst prognosis. Complete removal of the tumor by means of wide excision as primary treatment seemed to be the most important factor in decreasing the morbidity and mortality rates.

Epithelioid Schwannoma: Diagnosis by Electron Microscopy

The clinical, gross, and light microscopic features of two epithelioid tumors were not typical of either benign or malignant schwannoma. Both tumors displayed long, enveloping cytoplasmic processes that were outlined by layers of discrete basal lamina. Long-spaced collagen was found in one case. These well-developed electron microscopic features are those that are commonly encountered in benign Schwann cell tumors. Although one patient died postoperatively, the other is alive and well 12 months after surgery. The extent to which ultrastructural data can have an impact on the evaluation of Schwann cell tumors is unknown but requires further study.

Light microscopic and ultrastructural observations of a metastasizing malignant epithelioid schwannoma

The light microscopy and ultrastructure of a malignant epithelioid schwannoma are described. Characteristic cells resembling perineural elements with various degrees of differentiation were observed. Primitive epithelioid cells contained scant ergastoplasm, and few tubules and filaments, but did have abundant free ribosomes and Golgi membranes. Also noted were junctional complexes and focal fusion of plasma membranes, basal laminae were absent. Better differentiated cells were completely limited by a well-developed basal membrane and had an abundance of intracytoplasmic filaments and multiple pinocytotic vesicles. The intercellular ground substance was composed of numerous fine collagen fibrils and amorphous, basement membrane-like, electron-dense material. A striking ultrastructural similarity of the tumor cells to those encountered in ethylnitrosourea-induced malignant schwannomas in rats was noteworthy.