Immunohistochemical subclassification of thyroid tumors with a prominent hyalinizing trabecular pattern

The purpose of this study was to evaluate the immunohistochemical characteristics of thyroid tumors with a prominent hyalinizing trabecular pattern (TTHTP). Immunohistochemical stains for thyroid transcription factor 1 (TTF-1), thyroglobulin, CD56, cytokeratin (CK) 19, galectin-3, and Ki-67 were performed on 16 cases of TTHTP. All TTHTPs were positive for TTF-1 and thyroglobulin, and nine cases expressed CD56 and Ki-67. Of these nine cases, seven satisfied the strict criteria of Carney, and four cases were positive for CK19 or/and galectin-3 and negative for Ki-67 and CD56. The remaining three cases had no Ki-67, CD56, CK19 or galectin-3 expression. All TTHTPs meeting the criteria of Carney were hyalinizing trabecular tumors (HTT), and TTHTPs which did not satisfy the criteria of Carney were subclassified according to the immunohistochemical results as the HTT type [Ki-67 (+) and CD56 (+)], papillary thyroid carcinoma (PTC) type [CK19 or galectin-3 (+)/Ki-67 (-) and CD56 (-)], or null type [Ki-67 (-), CD56 (-), CK19 (-) and galectin-3 (-)]. TTHTPs with typical histologic features and/or with typical immunohistochemical manifestations can be categorized as HTT, and the remaining TTHTPs should be categorized as the PTC or null type.ope