title: Solitary fibrous tumor of the thymus with variegated epithelial components.
abstract: Solitary fibrous tumor is a rare mesenchymal neoplasm, characterized by peculiar histological features composed by the proliferation of spindle cells in "patternless pattern". Although it has been known to sometimes be accompanied by epithelioid cells, the presence of a well-formed epithelial structure is far more rare. We describe herein the case of a 60-year-old female with the radiological finding of a single nodular lesion in the anterior mediastinum. Histopathological examination of the surgically resected specimen led to the diagnosis of solitary fibrous tumor of the thymus with a spectrum of well-formed epithelial components: i) glandular structure, reminiscent of breast or eccrine gland, ii) neural tube-like structure, and iii) clusters of endocrine-like cells. Immunohistochemical analysis revealed that the spindle cells expressed CD34, vimentin, bcl-2 and Stat-6, but not keratin (cytokeratin-AE1/AE3) or epithelial membrane antigen. In contrast, the epithelial components lost expression of most of these marker proteins, including Stat-6, but continued to express vimentin and strongly expressed keratin. Since no relevant past literature was found, the current case could be interpreted as a unique and previously undescribed variant of solitary fibrous tumor comprising conventional spindle cells with a spectrum of well-formed epithelial components. Pathogenesis that may have given rise to these variegated mixtures of spindle cells and epithelial components in a single tumor is also discussed.
authors.affiliation: Department of Thoracic Surgery, Saitama Medical Center, Jichi Medical University Saitama, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Tsubochi
authors.affiliation: Department of Thoracic Surgery, Saitama Medical Center, Jichi Medical University Saitama, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Endo
authors.affiliation: Department of Thoracic Surgery, Saitama Medical Center, Jichi Medical University Saitama, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Sogabe
authors.affiliation: Department of Thoracic Surgery, Saitama Medical Center, Jichi Medical University Saitama, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Endo
authors.affiliation: Department of Diagnostic Pathology, Kitasato Institute Hospital Tokyo, Japan.
authors.forename: Shojiroh
authors.initials: S
authors.lastname: Morinaga
authors.affiliation: Department of Pathology, Saitama Medical Center, Jichi Medical University Saitama, Japan.
authors.forename: Yoh
authors.initials: Y
authors.lastname: Dobashi
mesh_terms: D018952:Antigens, CD34 / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000378:metabolism; D008875:Middle Aged; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D050800:STAT6 Transcription Factor / Q000378:metabolism; D054364:Solitary Fibrous Tumors / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D008941:Spindle Apparatus / Q000378:metabolism; D013953:Thymus Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D014746:Vimentin / Q000378:metabolism*
chemical_list: D018952:Antigens, CD34; D014408:Biomarkers, Tumor; D019253:Proto-Oncogene Proteins c-bcl-2; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D014746:Vimentin; D007633:Keratins
keywords: Solitary fibrous tumor; endocrine cells; epithelial component; epithelioid solitary fibrous tumor; gland; neural tube