title: Malignant primitive neuroectodermal tumor presenting as a scalp nodule.
abstract: 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.
authors.affiliation: Department of Medicine, Hartford Hospital, Connecticut.
authors.forename: C M
authors.initials: CM
authors.lastname: Jacinto
authors.forename: J M
authors.initials: JM
authors.lastname: Grant-Kels
authors.forename: D R
authors.initials: DR
authors.lastname: Knibbs
authors.forename: L A
authors.initials: LA
authors.lastname: Daman
authors.forename: R J
authors.initials: RJ
authors.lastname: Piorkowski
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D009364:Neoplasm Recurrence, Local; D009442:Neurilemmoma / Q000473:pathology*; D010751:Phosphopyruvate Hydratase / Q000032:analysis; D009418:S100 Proteins / Q000032:analysis; D012535:Scalp / Q000473:pathology; D012536:Scalp Dermatoses / Q000473:pathology*; D012878:Skin Neoplasms / Q000473:pathology*; D014746:Vimentin / Q000032:analysis
chemical_list: D009418:S100 Proteins; D014746:Vimentin; D010751:Phosphopyruvate Hydratase