title: Loss of cytokeratin 20 and acquisition of thyroid transcription factor-1 expression in a merkel cell carcinoma metastasis to the brain.
abstract: Merkel cell carcinoma (MCC) is recognized by its morphologic features and by its classic immunophenotypic properties. Although MCCs demonstrating nonclassic immunoreactivities have been described, a case documenting a change in immunophenotype during the course of disease progression has not been previously reported. We report a case of MCC that initially demonstrated cytokeratin 20 positivity but lost expression in subsequent metastases. Likewise, thyroid transcription factor-1 was initially negative in the tumor but expression was present in metastatic lesions.
authors.affiliation: Departments of *Pathology, †Neurosurgery, ‡Otolaryngology-Head and Neck Surgery, and §Dermatology, University of Arkansas for Medical Sciences, Little Rock, AR.
authors.forename: Sara C
authors.initials: SC
authors.lastname: Shalin
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cifarelli
authors.forename: James Y
authors.initials: JY
authors.lastname: Suen
authors.forename: Ling
authors.initials: L
authors.lastname: Gao
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D001706:Biopsy; D001932:Brain Neoplasms / Q000737:chemistry* / Q000556:secondary* / Q000628:therapy; D015266:Carcinoma, Merkel Cell / Q000737:chemistry* / Q000556:secondary* / Q000628:therapy; D018450:Disease Progression; D006801:Humans; D007150:Immunohistochemistry; D053554:Keratin-20 / Q000032:analysis; D008297:Male; D009687:Nuclear Proteins / Q000032:analysis*; D011237:Predictive Value of Tests; D012878:Skin Neoplasms / Q000737:chemistry* / Q000473:pathology / Q000628:therapy; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; C507499:KRT20 protein, human; D053554:Keratin-20; C000614412:NKX2-1 protein, human; D009687:Nuclear Proteins; D000074482:Thyroid Nuclear Factor 1; D014157:Transcription Factors