Cases reported "Nevus, Pigmented"

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1/6. Intradermal melanocytic nevus with prominent schwannian differentiation.

    Features of peripheral nerve sheath differentiation such as neuroid cords, nerve corpuscles, fascicle-like structures, and, exceptionally, palisading have been reported in melanocytic nevi. We report an intradermal melanocytic nevus with prominent Verocay-like bodies. The upper portion of the neoplasm was composed of typical round intradermal nevus cells, many of which were pigmented. Within the deeper portion, there was a nonpigmented spindle cell proliferation with prominent Verocay bodies, simulating a neurilemmoma. Typical nevus nests merged with neurilemmoma-like areas. The entire lesion stained positively for S-100 and Mart-1 proteins and negatively for HMB-45 stain. Diffuse Mart-1 positivity excluded a collision of a melanocytic lesion with a neurilemmoma. The histopathologic features of this nevus further support a close relation between nevus cells and schwann cells.
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keywords = schwann
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2/6. Congenital melanocytic naevus with associated neurofibroma and schwannoma-like change.

    Congenital melanocytic naevus and neurofibromatosis type 1 are distinct clinical entities. A diagnosis of neurofibromatosis is difficult to make in the presence of a congenital melanocytic naevus because nodules may arise in the naevus that have similar histopathological appearances to neurofibromata. A case is reported where nodules arising from a naevus were examined histologically and were found to have neurofibroma and schwannoma like elements but strong positivity for S100 protein in keeping with dermal melanocytes. Lisch nodules were also said to be found in the patient but may represent nodular naevi of the irides. It is important that histopathological findings are interpreted within a clinical context and S100 protein immunohistochemical stain is valuable in helping to differentiate these two conditions.
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ranking = 1.25
keywords = schwann
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3/6. Cellular blue nevus ("melanocytoma") of the spinal meninges: electron microscopic and immunohistochemical features.

    A primary cellular blue nevus (melanocytoma) of the spinal canal in a 21-year-old woman is reported. light microscopic examination revealed a melanotic neoplasm with histological patterns resembling schwannoma, dermal nevi, and neuroblastic-like tumor. The ultrastructural features of the neoplastic cells were similar to those in dermal blue nevi and melanomas. There was no evidence of arachnoidal cell differentiation. immunohistochemistry revealed positive reactions for S-100 protein and neuron-specific enolase in many cells and no reactions for glial fibrillary acidic protein, cytokeratins, epithelial membrane antigen, 70-kD neurofilament protein, or Leu-7. vimentin was strongly positive in the melanocytic cells as well as in the arachnoidal cells of involved meninges. The ultrastructural and immunohistochemical features support the nevoid nature of this tumor, which is frequently mislabeled as "melanotic meningioma."
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keywords = schwann
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4/6. The oral blue nevus: histogenetic implications of its ultrastructural features.

    Three cases of oral blue nevus are presented. A comparison of the ultrastructural features of blue nevus cells with those of schwannoma cells indicates that, among other similarities, both exhibit a surrounding external lamina (basement membrane). The significant difference is that blue nevus cells are capable of synthesizing melanin as evidenced by the presence of the entire melanosome maturation sequence within their cytoplasm, a feature not seen in the cells of schwannomas. This fundamental difference suggests that blue nevus cells are more closely related to melanocytes, although they possess some of the characteristics of schwann cells.
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keywords = schwann
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5/6. Malignant schwannoma with melanocytic and neuroepithelial differentiation in an infant with congenital giant melanocytic nevus: a complex neurocristopathy.

    We describe an infant girl, born with a pigmented giant nevus, who developed a malignant schwannoma in the retroperitoneum at 16 months of age. At birth the nevus covered over 50% of her body and histologically was a compound nevus with extension into the deep dermis surrounding dermal appendages. The malignant schwannoma was biphasic with areas composed of spindle and round cells. Ultrastructurally, the majority of the tumor cells exhibited a Schwann cell phenotype, but neuroepithelial and melanocytic cells were identified as well. We believe that this constellation of findings represents a form of neurocristopathy. Neurocristopathy, as defined by Bolande (Hum Pathol 5:409-429, 1974), is a disease that results from aberrations in the migration, growth, or cytodifferentiation of neural crest tissues. These diseases may be simple (a singular pathologic process, usually localized) or complex (multiple neuroectodermal lesions). We report this case because the occurrence of retroperitoneal malignant schwannoma arising in a 16-month-old infant born with a pigmented giant nevus is unique, and may represent a previously undescribed form of a complex neurocristopathy.
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ranking = 1.75
keywords = schwann
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6/6. Spinal meningeal melanocytoma. Case report and analysis of diagnostic criteria.

    A case of cervical juxtamedullary meningeal melanocytoma is presented along with results of careful neuroradiological and pathological examinations. The authors review the previous literature and discuss the problems related to the intriguing diagnosis of this very rare entity. CT and MRI show variable appearances due to different degrees of melanization and do not reliably allow us to distinguish meningeal melanocytomas from other pigmented tumors. Pathological examination of the tumor is critical for diagnosis, but it absolutely must comprise electron microscopy and immunohistochemistry. Immunohistochemical and ultrastructural criteria are thus proposed to distinguish meningeal melanocytoma from pigmented meningioma or schwannoma and malignant melanoma (primary or secondary).
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keywords = schwann
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