The columnar cell variant of papillary carcinoma (CCVPC) of the thyroid is a very rare variant of thyroid papillary carcinoma (PTC). These tumors have more potential for metastasis than PTC and show poor prognosis. These tumors, sharing histopathologic characteristics different from those of PTC, are characterized by columnar epithelium lining papillary and/or follicular structures and marked nuclear stratification. But the tumors rarely may contain classic nuclear features of PTC and histologic changes reminiscent of those in early secretory endometrium and can be confused with metastatic adenocarcinomas.
Our case was a 40 year old woman presenting with bilateral solid thyroid nodules. Fine needle aspiration of these nodules was diagnosed as papillary carcinoma. On gross examination, there were multiple solid nodules, the biggest one is 2 cm in diameter and encapsulated and the others with irregular margins in right lobe, isthmus, and left lobe. The histopathologic examination showed a mixture of papillary and follicular patterns lined by pseudostratified columnar epithelium and classical nuclear features of PTC were focally present in the tumor. In addition to capsular invasion, vascular invasion and widespread extension of the tumor to the perithyroideal soft tissue were present. In immunohistochemical study, the tumor cells showed diffuse TTF-1 positivity whereas CEA was negative. Therefore, metastatic adenocarcinomnas were not considered in the differential diagnosis.
We think it is worthy to report this case because of its very rare occurrence, confusable with metastases and aggressive behavior.