Hyalinizing trabecular adenoma of the thyroid gland

Hyalinizing trabecular adenoma (HTA) is a rare primary thyroid neoplasm. Ever since its initial descriptions, controversy has surrounded the lesion, particularly in regard to its malignant potential and most appropriate terminology. HTA shares many features with medullary thyroid carcinoma and particularly papillary thyroid carcinoma, making it an especially treacherous lesion on fine-needle aspiration (FNA). This manuscript reviews the history and pathologic features of HTA, with particular attention to cytologic findings and differential diagnosis.