Hyalinizing trabecular tumor of the thyroid: an update

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Hyalinizing trabecular tumor (HTT) is a rare thyroid neoplasm originating from follicular cells.
• It presents a trabecular growth pattern with significant intratrabecular hyalinization.
• HTT shares morphological similarities with paraganglioma, medullary thyroid carcinoma, and papillary thyroid carcinoma (PTC).

Purpose of the Study:

• To investigate the molecular characteristics and potential relationship of HTT to other thyroid tumors.
• To clarify the diagnostic criteria and malignant potential of HTT.

Main Methods:

• Morphological and architectural analysis.
• Immunohistochemical staining, including MIB1.
• Molecular analysis for RET/PTC, RAS, and BRAF mutations.

Main Results:

• HTT exhibits RET/PTC1 translocations, similar to PTC, but lacks RAS or BRAF mutations.
• Tumor cells show characteristic strong peripheral cytoplasmic and membranous MIB1 staining, a unique feature among thyroid neoplasms.
• While malignant cases exist, HTT is generally considered benign or of extremely low malignant potential.

Conclusions:

• The presence of RET alterations in HTT warrants further investigation into its relationship with PTC.
• The unique MIB1 staining pattern is a key diagnostic feature for HTT.
• HTT should be classified as a benign neoplasm or one with very low malignant potential.