Histopathological Features of Pendred Syndrome Thyroids Align with Differences in the Expression of Thyroid-Specific Markers, Apical Iodide Transporters, and Ciliogenesis Process.

Pendred syndrome (PDS) is an autosomal recessive disorder caused by mutations in the gene that encodes pendrin. Pendred thyroid tissue is supposedly altered by the absence of functional pendrin, but it is still unknown whether other iodide exchangers could compensate for the loss of the protein. Moreover, we have recently described that primary cilium, a conserved structure present at the apical surface of normal follicular cells, suffers different alterations in functional thyroid diseases. We aimed (1) to better understand the histopathological changes experienced by PDS thyroids, (2) to analyze the expression of different thyroid-specific genes and alternative iodide transporters and, finally, (3) to determine whether those changes may alter the morphological pattern of primary cilia in follicular cells. Thyroid samples from a series of four PDS patients were analyzed by immunohistochemistry, double immunofluorescence, and morphometry to evaluate changes in primary cilia frequency and length. We found thyroid follicular nodular disease in all PDS thyroids, frequently in association with follicular adenomas. There were only slight changes in the expression of thyroid-specific markers. Although no positivity for pendrin was found, cytoplasmic immunostaining for ANO-1, CLC-5, and CFTR was stronger in diffuse hyperplastic areas when compared to areas with highly cellular follicular nodules (HCFNs). HCFNs and follicular adenomas always showed diminished ciliary frequency and length. Our results suggest a direct relationship between the absence of functional pendrin and the loss of the normal thyroid architecture in PDS patients, which was also accompanied by differences in the expression of specific immunohistochemical markers and altered ciliogenesis. The present data may help the pathologist in screening for PDS.