CDX2 expression in columnar cell variant of papillary thyroid carcinoma

The columnar cell variant of papillary thyroid carcinoma (CCV-PTC) is a rare subtype of PTC that exhibits morphologic features often described as reminiscent of secretory endometrium or colonic adenomas/adenocarcinomas. CDX2, a nuclear transcription factor, is important for intestinal development. It is normally expressed in intestinal epithelium and is also detected in adenoma and adenocarcinomas of the gastrointestinal tract; however, it has also been reported in tumors of other sites with intestinal-type morphologic features. We evaluated CDX2 expression in CCV-PTC and in a thyroid tissue microarray composed of various benign and malignant thyroid lesions. CDX2 expression was identified in 6 (55%) of 11 cases of CCV-PTC, but not in any other benign and malignant thyroid lesions. We conclude that CDX2 is selectively expressed in CCV-PTC and can be used in distinguishing it from other variants of PTC with overlapping morphologic features.