title: p63 expression in solid cell nests of the thyroid: further evidence for a stem cell origin.
abstract: Solid cell nests of the thyroid are embryonic remnants of endodermal origin that may be difficult to distinguish from squamous metaplasia, metastatic squamous carcinoma, papillary microcarcinoma, medullary carcinoma, and C-cell hyperplasia. These embryonic structures are composed of main cells and C-cells; cystic structures and mixed follicles are sometimes observed intermingled with solid cell nests. Recently, p63, a p53 homologue that is consistently expressed in basal/stem cells of stratified epithelia and plays a major role in triggering the differentiation of some specific cell lineages, has been characterized. We evaluated the immunohistochemical expression of p63, cytokeratins (CAM 5.2, AE1/AE3, 34betaE12, 7, and 20), carcinoembryonic antigen, thyroid transcription factor 1 (TTF-1), thyroglobulin, and calcitonin using the streptavidin-biotin-peroxidase complex technique in 6 bona fide solid cell nests. We observed that main cells of solid cell nests are strongly decorated by p63, while C-cells and all other thyroid structures were consistently negative. Moreover, main cells expressed carcinoembryonic antigen and all cytokeratins but cytokeratin 20 and lacked TTF-1, thyroglobulin and calcitonin. In contrast to this, C-cells of solid cell nests were immunoreactive for calcitonin, CAM 5.2, AE1/AE3, and cytokeratin 7; focal immunoreactivity for TTF-1 was also observed in some C-cells. We conclude that main cells of the solid cell nests display a basal/stem cell phenotype (p63 and basal cytokeratin positivity), whereas C-cells show features of parafollicular differentiation. We conclude, furthermore, that p63 antibodies may help in distinguishing solid cell nests from their mimics.
authors.affiliation: Institute of Molecular Pathology and Immunology, University of Porto, Porto, Portugal.
authors.forename: Jorge S
authors.initials: JS
authors.lastname: Reis-Filho
authors.forename: Ana
authors.initials: A
authors.lastname: Preto
authors.forename: Paula
authors.initials: P
authors.lastname: Soares
authors.forename: Sara
authors.initials: S
authors.lastname: Ricardo
authors.forename: José
authors.initials: J
authors.lastname: Cameselle-Teijeiro
authors.forename: Manuel
authors.initials: M
authors.lastname: Sobrinho-Simões
mesh_terms: D000236:Adenoma / Q000378:metabolism* / Q000473:pathology; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002272:Carcinoembryonic Antigen / Q000378:metabolism; D002291:Carcinoma, Papillary / Q000378:metabolism* / Q000473:pathology; D004268:DNA-Binding Proteins; D005260:Female; D016147:Genes, Tumor Suppressor; D006801:Humans; D007124:Immunoenzyme Techniques; D007633:Keratins / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins; D008875:Middle Aged; D010750:Phosphoproteins / Q000378:metabolism*; D013234:Stem Cells / Q000378:metabolism* / Q000473:pathology; D013964:Thyroid Neoplasms / Q000378:metabolism* / Q000473:pathology; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins
chemical_list: D014408:Biomarkers, Tumor; C081876:CKAP4 protein, human; D002272:Carcinoembryonic Antigen; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D007633:Keratins