A Case Report of Thyroid Hyalinizing Trabecular Adenoma Suspected by Preoperative Cytodiagnosis

Abstract

The first report of a hyalinizing trabecular tumor, a rare form of thyroid tumor, was made by JA Carney. A problem with cytodiagnosis is the difficulty of differentiating hyalinizing trabecular adenoma from papillary carcinoma or medullar carcinoma. Here, we report a case in which diagnosis of hyalinizing trabecular tumor was possible preoperatively. The patient was a 47-year-old woman. Medical examination suggested the presence of a mass at the right lobe of the thyroid. Neck ultrasonography revealed a solid and well-defined mass sized 9 mm × 14 mm × 16 mm. Fine needle aspiration cytology found follicular epithelial cells containing intranuclear inclusion bodies. However, the cells had partly unclear cytoplasm and were clumped. Such features are not typical of thyroid papillary carcinoma. The patient underwent an operation involving right lobe resection and paratracheal lymph node dissection. Pathological diagnosis pointed to a hyalinizing trabecular adenoma. Determination on whether this tumor is benign or malignant is still inconclusive, and in the 8th edition of “General Rules for the Description of Thyroid Cancer” this case has been classified as “another tumor.” The important points for differentiating tumors are the form of the tumor cells, and the results and locations derived by immunohistochemistry.