[593] CDX2 Is Rarely Expressed in Columnar Cell Variant of Papillary Thyroid Carcinoma: A Study of Ten Cases.

Victoria Sujoy, Andre Pinto, Christina M Kovacs, Vania Nose. Jackson Memorial Hospital/University of Miami, Miami, FL

Background: Columnar cell variant is a recognized rare variant of papillary thyroid carcinoma (PTC) associated with an uncertain clinical course. This variant has been regarded as a more aggressive form in comparison to the more common classical and follicular variants. These tumors have morphological resemblance with colonic adenocarcinoma. CDX2, a transcription factor of the caudal homeobox family, plays a key role in intestinal development and differentiation and it is widely used as a marker to detect adenocarcinoma of intestinal and colonic origin. CDX2 has been rarely reported in PTC. Only a single report of three cases of columnar cell variant of PTC has suggested that CDX2 should be considered a novel marker for diagnosis of this entity.
Design: We studied ten cases of columnar cell variant of papillary thyroid carcinoma. The histological, architectural, and cytological features fulfilled the diagnostic criteria of the columnar cell variant of papillary thyroid carcinoma as defined by the current WHO classification including neoplastic follicular cells with basally pseudostratified, hyperchromatic nuclei with eosinophilic-to-clear cytoplasm and supranuclear and/or subnuclear cytoplasmic vacuoles. Ten patients (6M:4F) ranging from 32 to 90 years of age (mean 58.3 years) presented with tumors classified as indolent (4 cases) or aggressive (6 cases); 3 with BRAFV600E mutation. All cases were β-Catenin negative. The Ki-67 proliferative index was up to 50%. All cases were TTF-1 positive.
Using paraffin embedded blocks, immunohistochemistry for CDX2 (mouse monoclonal to CDX2 (CDX2-88), 1:50 dilution; Biogenex Laboratories) was performed to evaluate the reactivity of this antibody to this variant of PTC.
Results: Nuclear positivity for CDX2 was detected in one out of the ten cases studied (10%), the other nine cases did not express CDX2.
Conclusions: Only one of our cases showed nuclear positivity for CDX2, therefore our study failed to confirm this as a marker for columnar cell variant of papillary thyroid carcinoma. The absence of CDX2 in the majority of the cases does not support the theory of CDX2 playing a role in the intestinal phenotype of these tumors.
The use of CDX2 as an indicator of this rare variant of thyroid cancer should be considered with caution based on our study.
Category: Endocrine

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 37, Tuesday Afternoon

 

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