Endocrinol Metab > Volume 23(5); 2008 > Article
Journal of Korean Endocrine Society 2008;23(5):327-331.
DOI: https://doi.org/10.3803/jkes.2008.23.5.327    Published online October 1, 2008.
A Case of Hyalinizing Trabecular Tumor of the Thyroid Gland Misdiagnosed as Medullary Carcinoma at Cytologic Examination.
Jae Joon Han, Yun Jung Lee, Moon Chan Choi, Mikwang Kwon, Suk Chon, Juhie Lee
1Department of Endocrinology and Metabolism, Kyung Hee University School of Medicine, Korea.
2Research Institute of Endocrinology, Kyung Hee University School of Medicine, Korea.
3Department of Pathology, Kyung Hee University School of Medicine, Korea.
A hyalinizing trabecular tumor (HTT) is a rare benign thyroid tumor that can present as a solitary thyroid nodule, a prominent nodule in a multinodular goiter, or as an incidental finding within a thyroidectomy specimen. The clinical importance of this entity is that it is frequently misdiagnosed as papillary carcinoma or medullary carcinoma on fine-needle aspiration cytology or histopathologic examination. The cytology of HTT is characterized by hypercellularity, nuclear grooves, nuclear pseudoinclusions, and powdery chromatin of the tumor cells, which is frequently seen in papillary carcinomas. The histologic findings of the tumor show polygonal and spindle cells arranged in a trabecular growth pattern with the presence of a variable hyalinized stroma. Calcitonin and other neuroendocrine markers can be used to differentiate HTT from medullary carcinoma. MIB-1, galectin-3, or other cytokeratin markers help to exclude papillary carcinoma. We report a patient with a thyroid tumor misdiagnosed as a medullary carcinoma on fine-needle aspiration and finally diagnosed as HTT after total thyroidectomy and immunohistochemical examination.
Key Words: fine needle aspiration, hyalinizing trabecular tumor, thyroid nodules

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