Immunoexpression of MUC1 in papillary thyroid carcinoma: An association with aberrant expression of β-catenin and cyclin D1 overexpression

MUC1 mucin is a multifunctional glycoprotein expressed in a variety of normal human epithelial tissues and cancers. Besides mucin's functioning in the mechanical and chemical protection of cells, it can also mediate signal transduction through the β-catenin and MAP kinase pathways leading in some instances to more aggressive tumor behavior. This study examined the immunohistochemical expression of MUC1 in 209 thyroid carcinomas of different histotypes, size and morphological features of aggressiveness. Data were correlated with an aberrant β-catenin expression and cyclin D1 overexpression. The cytoplasmic MUC1 expression was elevated in the tall, columnar cell, oncocytic (100%) and Warthin-like (78%) variants of papillary thyroid carcinomas (PTC), conventional PTC (61%), and papillary microcarcinoma (PMC) with conventional growth pattern (52%) compared with the follicular variant of PTC (27%) and PMC with the follicular architecture (13%). In PMCs, MUC1 expression appeared to be proportional to tumor size. The cytoplasmic MUC1 accumulation did not associate with any of clinicopathological features of the tumors but rather with lymphoid infiltration although inflammation alone did not strictly determine MUC1 overexpression. MUC1 pattern strongly correlated with β-catenin/cyclin D1 immunostaining implying MUC1 involvement in the Wnt cascade in thyroid cancer.