[561] CDX2 Expression in Columnar Cell Variant of Papillary Thyroid Carcinoma

ML Enriquez, LB Ende, PJ Zhang, KT Montone, VA LiVolsi. Hospital of the University of Pennsylvania, Philadelphia, PA

Background: Columnar cell variant of papillary thyroid cacinoma is a rare, aggressive tumor that exhibits elongated and enlarged nuclei and nuclear stratification, often without the typical nuclear characteristics seen in papillary carcinomas of the thyroid. The morphology of columnar cell variant is often reminiscent of colonic adenocarcinomas. CDX2 is known to play a critical role in the embryologic development of the GI tract and establishment of the intestinal cell phenotype. It is also highly expressed in GI adenocarcinomas, but not or rarely in tumors of other origins. CDX2 has been reported rarely in papillary carcinoma of the thyroid but has not yet been evaluated in the columnar cell variant, which shares morphologic similarity with GI tumors.
Design: Three cases of columnar cell variant of thyroid carcinoma were studied. All cases were located in thyroid and tested positive for TTF-1 at the time of diagnosis. Paraffin section of each case was stained with a mouse monoclonal antibody against CDX-2 (clone CDX2-88, Biogenex, San Ramon, CA) on Leica Microsystems' Bondmax autostainer after sections heated in a 70°C oven for 1 hour.
Results: Diffuse nuclear CDX2 reactivity was detected in all three columnar cell variants, but not in the adjacent non-neoplastic thyroid tissue.
Conclusions: CDX2 is a homeobox gene that encodes an intestine-specific transcription factor that is expressed in epithelial cells throughout the intestine. CDX2 has been used as a sensitive and specific marker for colonic adenocarcinomas. Previously, a single case (papillary type) of 30 thyroid cancers was found to be CDX2 positive. Our finding of all three cases of columnar cell variant staining positively for CDX2 is novel, and suggests that the genetic basis as well as the intestinal-type morphology seen in this rare thyroid tumor may be due in part to CDX2 expression. This finding may have important implications for understanding the molecular basis of columnar cell variant of papillary thyroid carcinoma. Columnar cell variants of thyroid carcinoma should be included in the differential diagnosis of carcinoma with columnar cell morphology and CDX2 reactivity.
Category: Endocrine

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 48, Tuesday Afternoon


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