ABSTRACT

Hyalinizing thyroid trabecular tumor (HTTT) is a rare benign encapsulated neoplasm of the thyroid gland that was first described by Carney in 1987. Besides its morphological variations this thyroid lesion is histologically characterized by a trabecular growth pattern interspersed with hyaline material. As the differential diagnosis is complicated because of its similarity with papillary and medullary carcinomas of the thyroid immunohistochemical studies must be performed to confirm the diagnosis. Here we present a case that was initially misdiagnosed as medullary carcinoma of the thyroid. Subsequent histopathological and immunohistochemical evaluations (negative for calcitonin, chromogranin, neuron-specific enolase and synaptophysin, and positive for thyroglobulin) of the specimen, including completion left total thyroidectomy material, resulted in the final diagnosis of HTTT.