Abstract

Hyalinizing trabecular adenoma of the thyroid gland is a rare benign neoplasm. This can be confused with papillary carcinoma and thyroid medullary carcinoma in cytology from the permanent sections analysed. The female patient was clinically diagnosed as having euthyroid and radioactive iodine as a result of the scan performed which revealed a solitary “cold” nodule in right lobe. The hypocellulary TIIAB consisted of cells that were features of papillar carcinoma. A final diagnosis of the TIIAB was reported as a suspicious papillary carcinomas of the thyroid. A total thyroidectomy was performed and requested to be frozen. In the frozen section analysed, It was thought to be compatible with papillary carcinoma due to having solid and trabecular patterns in the hyalinizing stroma, nucleer pseodoinclusions and microcalsifications. Histologically, prominent nesting, trabecular growth patterns and a hyaline stroma were found. In the permanent sections analysed, the tumor exhibited clear margins of thin, fibrous capsule cells that were features of papillar carcinoma. Tumor cells were diffusely positive for thyroglobulin, but negative for staining with antibodies to HBME-1, CK19 and calcitonin. The case was reported as“hyalinizing trabecular adenoma”. This rare tumor is presented to draw attention to the features of cytology, morphologic and immunohistochemical.