title: Aberrant tyrosinase expression in an atypical fibroxanthoma: A case report.
abstract: Atypical fibroxanthoma (AFX) is a histologic mimicker of a variety of spindle cell neoplasms, and careful microscopic and immunohistochemical evaluation is critical in establishing the correct diagnosis. Here we report the histologic and immunohistochemical work up of a 1 cm nodule involving the left dorsal hand of a 66-year-old patient. Light microscopy revealed fascicles of spindled and pleomorphic cells within the dermis showing increased mitotic activity occurring in the background of sun-damaged skin. There were numerous multinucleated cells with hyperchromatic nuclei and ample finely vacuolated or foamy cytoplasms. There was strong and diffuse CD10 and patchy CD68 expression among the spindled cells and multinucleated cells. The neoplastic cells did not show immunoreactivity against S100, p75-NGFR, HMB-45 or a panel of keratinocytic, vascular and smooth muscle markers. Tyrosinase and Melan-A were not expressed within the spindle cell component of this neoplasm; however, there was tyrosinase expression among numerous multinucleated giant cells. Melan-A expression was also observed among rare multinucleated giant cells. Tyrosinase expression has not previously been reported in AFX.
authors.affiliation: Rutgers University - New Jersey Medical School, Newark, New Jersey.
authors.forename: Amy
authors.initials: A
authors.lastname: Weiss
authors.affiliation: Division of Dermatology, Rutgers University - New Jersey Medical School, Newark, New Jersey.
authors.forename: Vijay
authors.initials: V
authors.lastname: Vanchinathan
authors.affiliation: Division of Dermatology, Rutgers University - New Jersey Medical School, Newark, New Jersey.|Dermpath Diagnostics New York, Port Chester, New York.
authors.forename: Eun J
authors.identifier: http://orcid.org/0000-0001-9469-8654
authors.initials: EJ
authors.lastname: Kwon
mesh_terms: D000368:Aged; D020405:Dermis / Q000201:enzymology / Q000473:pathology; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D014442:Monophenol Monooxygenase / Q000096:biosynthesis*; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D012878:Skin Neoplasms / Q000201:enzymology / Q000473:pathology; D014973:Xanthomatosis / Q000201:enzymology / Q000473:pathology
chemical_list: D009363:Neoplasm Proteins; D014442:Monophenol Monooxygenase
keywords: MART-1; atypical fibroxanthoma; immunohistochemistry; melan-A; tyrosinase