Cytological characteristics of a case of the sporadic cribriform morular variant of papillary thyroid carcinoma

Abstract

Background : We report the cytologic findings in a case of the sporadic cribriform-morular variant of papillary thyroid cancer (CMV-PTC), findings that may be associated with its biological characteristics.

Case : A woman in the third decade of life came to our hospital with a chief complaint of an approximately 5-cm mass in the right lobe of her thyroid gland. Smears of aspirated thyroid tissue revealed a variable architectural pattern. The epithelial cells were arranged in stratified papillae, cribriform clusters, and monolayer sheets, some of which displayed cellular discohesion and spindling at the borders. Ovoid nuclei were characterized by coarse chromatin distribution, indistinct nucleoli, nuclear grooves, and a few cytoplasmic inclusions. We initially diagnosed the lesion as a PTC, but subsequent histological examination led to a final diagnosis of CMV-PTC. Review of the cytological smears revealed that some of the clusters lacked sharp anatomical borders or nuclear palisading. Individual cell morphology ranged from polygonal, tall columnar to fusiform. Immunochemistry revealed marked β-catenin accumulation in the nucleus and the cytoplasm of the tumor cells, whereas there was as decreased amount or no β-catenin in its normal membranous location.

Conclusion : The cell junctions at the edges of the clusters of CMV-PTC cells were loose, and solitary cells were conspicuous. We concluded that the weakened cell adhesion together with the intranuclear accumulation of β-catenin caused by the abnormal activation of the Wnt signaling pathway affect the cytological characteristics of CMV-PTCs.