Hyalinizing trabecular tumors of the thyroid are interesting but uncommon neoplasms. They have been classified as benign hyalinizing trabecular adenomas or malignant hyalinizing trabecular carcinomas. They share both epidemiologic and morphologic features with papillary carcinoma, and there has been much speculation about the relationship between these two entities. Because RET/PTC gene rearrangements are specific to papillary thyroid carcinoma, the authors examined the presence of RET/PTC-1, -2, and -3 in eight hyalinizing trabecular tumors using reverse transcription–polymerase chain reaction with Southern hybridization and immunohistochemistry. They detected the presence of a RET/PTC gene rearrangement in six of the eight hyalinizing trabecular tumors. This confirms the long-standing suspicion that hyalinizing trabecular tumors do indeed represent a morphologic variant of papillary carcinoma.
From the Department of Pathology and Laboratory Medicine and The Freeman Centre in Endocrine Oncology (C.C.C., L.R., S.L.A.), Mount Sinai Hospital, Toronto, and the Department of Pathology, University Health Network (S.L.B., C.M.M., S.L.A.), Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada.
Supported in part by the Saul A. Silverman Family Foundation and Temmy Latner/Dynacare.
Address correspondence and reprint requests to Sylvia L. Asa, MD, PhD, Department of Pathology, University Health Network, 610 University Ave., Toronto, Ontario M5G 2M9 Canada; e-mail: firstname.lastname@example.org