CDX2 Expression in Some Variants of Papillary Thyroid Carcinoma.

To the Editor The publication of the article of Enriquez et al 1 coincided with the final steps of our study on the expression of CDX2 in normal and neoplastic follicular-derived cells of the human thyroid gland. Enriquez et al 1 evaluated CDX2 expression in 11 cases of columnar cell variant (CCV) of papillary thyroid carcinoma (PTC) and in thyroid tissue microarrays (TMAs) composed of normal tissue, 38 cases of benign lesions (Hashimoto disease, Graves disease, lymphocytic thyroiditis, multinodular goiter, and papillary hyperplasia), and 33 samples of neoplastic conditions (8 follicular carcinomas, 9 conventional PTC, 2 tall cell variants of PTC, 2 poorly differentiated carcinomas, 6 anaplastic carcinomas, 4 medullary carcinomas, 4 Hürthle cell adenomas, and 2 follicular adenomas). Enriquez et al 1 identified CDX2 expression in 6 (55%) of the 11 cases of CCV of PTC, but not in any other benign or malignant thyroid lesions. They only found focal or diffuse CDX2 immunoreactivity in tumors with pure columnar cell morphologic features (6/9 cases) but not in 2 cases with only focal columnar cell/ mixed features. They concluded that CDX2 is selectively expressed in CCV of PTC and can be used to distinguish it from other variants of PTC with overlapping morphologic features. We used a TMA composed of 10% formalin-fixed, paraffin-embedded thyroid tissue samples: 50 follicular adenomas, 75 PTCs (35 classic subtype, 27 follicular variant, 4 solid variant, 3 tall cell variant, 2 diffuse sclerosing variant, 4 cribriform morular variant [CMV; 2 sporadic and 2 associated with familial adenomatous polyposis]), 48 follicular carcinomas (34 minimally invasive, 14 widely invasive), 15 poorly differentiated carcinomas (6 insular variant, 9 noninsular), 13 undifferentiated (anaplastic) carcinomas, and 15 normal thyroid tissue. The TMA was built using a tissue arrayer device (Beecher Instruments, Sun Prairie, WI), including duplicate 1.6-mm cores of each type of tissue per case. All 216 samples and additional controls were collected from files of the data were collected from the pathology reports and clinical files. The local ethics and scientific committees approved this study. H&E slides were simultaneously reviewed by 2 pathologists (J.C.-T. and L.A.-L.) and the tumors classified using the World Health Organization criteria 2 with the Turin proposal for poorly differentiated carcinomas 3 ; cases with doubtful PTC features were excluded. The immunohistochemical study was performed on 4-μm-thick paraffin sections of the TMA blocks using a peroxidase-conjugated dextran-labeled polymer (EnVision FLEX, Dako, Glostrup, Denmark) to avoid misinterpreting …