Hyalinizing trabecular adenoma of the thyroid--morphology and differential diagnosis

Hyalinizing trabecular adenoma (HTA) is a rare but distinct type of thyroid neoplasm. Its typical morphological features are trabecular arrangement of tumour cells and the prominent hyaline appearance. Although cases of HTA with vascular and/or capsular invasion have been described, the vast majority of tumours are benign. This article deals with the histological, cytological, immunohistochemical, and ultrastructural features of HTA. The pitfalls of fine-needle aspiration biopsy and intra-operative frozen section examination are described. Finally the differential diagnostic aspects of HTA are discussed.