title: Conventional spindle cell-type malignant peripheral nerve sheath tumor arising in a sporadic schwannoma.
abstract: Malignant peripheral nerve sheath tumor is a malignant tumor showing nerve sheath differentiation. Approximately one-half of malignant peripheral nerve sheath tumors arise from a benign peripheral nerve sheath tumor, which is commonly a neurofibroma in patients with neurofibromatosis type 1. Malignant peripheral nerve sheath tumor arising in a sporadic schwannoma of soft tissue is extremely rare. In this condition, malignant cells usually show epithelioid morphology, meeting the diagnostic criteria for epithelioid malignant peripheral nerve sheath tumor. Here, we present an extraordinary case of spindle cell-type malignant peripheral nerve sheath tumor arising in a schwannoma on the back of a 58-year-old woman without neurofibromatosis. The malignant component showed hypercellular spindle cell proliferation with high mitotic activities; in contrast, the benign component showed hypocellular spindle cell proliferation in a palisading pattern and with Verocay bodies. Immunohistochemical S-100 protein staining showed a clear contrast between the malignant (negative) and benign (positive) components, which was useful for differentiating cellular schwannoma. Recognizing this rare condition is helpful in the pathologic diagnosis of schwannoma showing cellular proliferation in part.
authors.affiliation: Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Endo
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Katsumi
authors.initials: K
authors.lastname: Harimaya
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kohashi
authors.forename: Takeaki
authors.initials: T
authors.lastname: Ishii
authors.forename: Nokitaka
authors.initials: N
authors.lastname: Setsu
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Oda
mesh_terms: D001415:Back / Q000473:pathology* / Q000601:surgery; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D018317:Nerve Sheath Neoplasms / Q000473:pathology* / Q000601:surgery; D009442:Neurilemmoma / Q000473:pathology* / Q000601:surgery; D012983:Soft Tissue Neoplasms / Q000473:pathology* / Q000601:surgery; D016896:Treatment Outcome
keywords: Malignant peripheral nerve sheath tumor; Malignant transformation; SMARCB1; Schwannoma