Histopathological Characterization and Whole Exome Sequencing of Ectopic Thyroid: Fetal Architecture in a Functional Ectopic Gland from Adult Patient

Ectopic thyroid results from a migration defect of the developing gland during embryogenesis causing congenital hypothyroidism. But it has also been detected in asymptomatic individuals. This study aimed to investigate the histopathological, functional, and genetic features of human ectopic thyroids. Six samples were histologically examined, and the expression of the specific thyroid proteins was assessed by immunohistochemistry. Two samples were submitted to whole exome sequencing. An oropharynx sample showed immature fetal architecture tissue with clusters or cords of oval thyrocytes and small folliclesone sample exhibited a normal thyroid pattern while four showed colloid goiter. All ectopic thyroids expressed the specific thyroid genes and T4 at similar locations to those observed in normal thyroid. No somatic mutations associated with ectopic thyroid were found. This is the first immature thyroid fetal tissue observed in an ectopic thyroid due to the arrest of structural differentiation early in the colloid stage of development that proved able to synthesize thyroid hormone but not to respond to TSH. Despite the ability of all ectopic thyroids to synthetize specific thyroid proteins and T4, at some point in life, it may be insufficient to support body growth leading to hypothyroidism, as observed in some of the patients.FAPESP Grant [2009/53840-0]Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Sao Paulo, Brazil [2010/12005-9, 2014/24549-4]Instituto da TiroideUniv Sao Paulo FMUSP, Fac Med, Cellular & Mol Endocrine Lab, Thyroid Unit,LIM 25, Ave Doutor Arnaldo 455, BR-01246904 Sao Paulo, SP, BrazilSao Paulo Publ Hlth Serv, Adolfo Lutz Inst, Av Dr Arnaldo 355, BR-01246000 Sao Paulo, SP, BrazilHead & Neck Surg Santa Catarina Hosp, Av Paulista 200, BR-01310000 Sao Paulo, SP, BrazilUNESP, Botucatu Sch Med, Dept Internal Med, Av Prof Montenegro,S-N Dist Rubiao Jr, BR-18618687 Botucatu, SP, BrazilHosp Pediat Dr Juan Garrahan, Serv Endocrinol, Combate Pozos 1881,C1245AAM, Buenos Aires, DF, ArgentinaUniv Estadual Campinas, Fac Ciencias Med, Dept Cirurgia, Disciplina Cirurgia Cabeca & Pescoco, R Tessalia Vieira Camargo 126, BR-13083887 Campinas, SP, BrazilUniv Fortaleza Unifor, Med Sch, Av Washington Soares 1321, BR-60811905 Fortaleza, CE, BrazilUniv Fed Sao Paulo UNIFESP, Postgrad Program Biotechnol, Pedro Toledo 669, BR-04039903 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Postgrad Programs Biotechnol & Struct & Funct Bio, Dept Ciencias Biol, Thyroid Mol Sci Lab,UNIFESP, Pedro Toledo 669, BR-04039903 Sao Paulo, SP, BrazilHosp Sirio Libanes, Mol Oncol Ctr, Rua Prof Daher Cutait 69, BR-01308060 Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, Postgrad Program Biotechnol, Pedro Toledo 669, BR-04039903 Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Postgrad Programs Biotechnol & Struct & Funct Bio, Dept Ciencias Biol, Thyroid Mol Sci Lab,UNIFESP, Pedro Toledo 669, BR-04039903 Sao Paulo, SP, BrazilFAPESP [2009/53840-0]FAPESP[2010/12005-9, 2014/24549-4]Web of Scienc