title: Clear cell tumor of the lung. Immunohistochemical and ultrastructural evidence of melanogenesis.
abstract: Clear cell tumors of the lung (CCTL) are rare neoplasms of uncertain differentiation. A previous study of eight CCTL demonstrated a lack of epithelial features, but their exact nature remained unknown. In the current study of nine CCTL, immunohistochemistry using preliminary enzymatic digestion showed strong reactivity with the antimelanocytic markers HMB-45 (seven cases) and HMB-50 (six cases) and focal positivity for S-100 (nine cases), neuron-specific enolase (three cases), synaptophysin (one case), and Leu-7 (one case). Staining for cytokeratin, epithelial membrane antigen, chromogranin, and glial fibrillary acid protein was uniformly negative. Frozen-section immunoreactivity for vimentin and the antimelanocytic monoclonal preparation NKI/BETEB was noted in the one CCTL for which snap-frozen tissue was available. Ultrastructural examination of three glutaraldehyde-fixed CCTL showed rare neoplastic cells containing the full spectrum of melanosomes in two, one of which also contained neurosecretory-type granules. Aberrant melanosomal forms were identified in the third case. Melanosomes were not identified in the remaining five CCTL studied from formalin- or paraffin-retrieved material. The findings indicate that CCTL exhibits melanocytic differentiation. This feature may be of considerable value in distinguishing CCTL from other clear cell neoplasms.
authors.affiliation: Department of Pathology, University of Virginia Health Sciences Center, Charlottesville 22908.
authors.forename: M J
authors.initials: MJ
authors.lastname: Gaffey
authors.forename: S E
authors.initials: SE
authors.lastname: Mills
authors.forename: R J
authors.initials: RJ
authors.lastname: Zarbo
authors.forename: L M
authors.initials: LM
authors.lastname: Weiss
authors.forename: A M
authors.initials: AM
authors.lastname: Gown
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D000943:Antigens, Differentiation / Q000378:metabolism; D018959:CD57 Antigens; D006801:Humans; D007150:Immunohistochemistry; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D008544:Melanocytes / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D009418:S100 Proteins / Q000378:metabolism; D016708:Synaptophysin
chemical_list: D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D018959:CD57 Antigens; D008565:Membrane Proteins; D009418:S100 Proteins; D016708:Synaptophysin; D010751:Phosphopyruvate Hydratase