Abstract
Background. Thyroid tumors are often difficult to histopathologically diagnose, especially follicular adenoma (FA) and follicular carcinoma (FC). Papillary carcinoma (PAC) has several histological subtypes. Periostin (PON), which is a non-collagenous extracellular matrix molecule, is related to tumor invasiveness. We aimed to elucidate the role of PON in thyroid tumors.Method. We collected 105 cases of thyroid nodules, which included cases of adenomatous goiter, FA, microcarcinoma (MIC), PAC, FC, poorly differentiated carcinoma (PDCa), and undifferentiated carcinoma (UCa), and immunohistochemically examined the PON expression patterns of these lesions. Results. PAC and MIC exhibited stromal PON deposition, especially in the solid/sclerosing subtype, whereas FA and FC showed weak deposition on the fibrous capsule. However, the invasive and/or extracapsular regions of microinvasive FC demonstrated quite strong PON expression.Except for it, we could not find any significantly histopathological differences between FA and FC. Although PDCa showed a similar PON expression pattern to PAC, UCa exhibited stromal PON deposition in its invasive portions and cytoplasmic expression in its carcinoma cells. Although there was only one case of UCa, it demonstrated strong PON immunopositivity. PAC and MIC showed similar patterns of stromal PON deposition, especially at the invasive front.Conclusions. PON plays a role in the invasion of thyroid carcinomas, especially PAC and UCa, whereas it acts as a barrier against the growth of tumor cells in FA and minimally invasive FC.
RASPoint Mutations and PAX8-PPARγ Rearrangement in Thyroid Tumors: Evidence for Distinct Molecular Pathways in Thyroid Follicular Carcinoma
