Hyalinizing trabecular tumour of the thyroid gland

By Jason Wasserman MD PhD FRCPC
January 27, 2024

A hyalinizing trabecular tumour (HTT) is an uncommon and unique type of growth found in the thyroid gland. The thyroid gland is located in your neck and produces hormones that control your metabolism. Most tumours behave in a benign (noncancerous) manner with only rare reports of tumours spreading to lymph nodes or other parts of the body.

Symptoms of hyalinizing trabecular tumour

Most patients with hyalinizing trabecular tumour will not experience any symptoms and the tumour will be found incidentally when imaging of the thyroid gland is performed for other reasons. However, some patients may notice a painless lump in the front of their neck.

Causes of hyalinizing trabecular tumour

The exact cause of hyalinizing trabecular tumour is not clearly understood. Like many tumours of the thyroid, it likely results from genetic changes in thyroid cells, but these changes are typically not associated with any known risk factors or genetic conditions.

Genetic alterations in hyalinizing trabecular tumour

Almost all hyalinizing trabecular tumours harbour a genetic alteration involving the genes GLIS1 or GLIS3. This alteration results in the GLIS (either 1 or 3) gene combining with another gene called PAX8 to form an abnormal fusion gene which drives the development of the tumour.

Who is at risk for developing a hyalinizing trabecular tumour?

Hyalinizing trabecular tumours can occur in adults of any age, but it is more commonly diagnosed in middle-aged women.

How is this diagnosis made?

Although the diagnosis may be suggested after a procedure called a fine needle aspiration biopsy (FNAB), the diagnosis of a hyalinizing trabecular tumour is typically only made after the entire tumour is removed and examined under a microscope by a pathologist.

Microscopic features

Under microscopic examination, a hyalinizing trabecular tumour is a well-circumscribed tumour typically separated from the surrounding normal thyroid gland by a thin band of tissue called a capsule. The tumour cells are larger and more pink than the normal follicular cells found in the thyroid gland and they are arranged in wide groups called trabeculae. A pink material called hyaline is often found within the trabeculae. The hyaline gives the tumour a pink look when examined on a routine hematoxylin and eosin (H&E) stained slide. The nucleus of the tumour cell is larger than normal and clear, and its outer membrane often appears convoluted or irregular. These changes are often described as being “papillary-like” because they resemble the changes seen in a type of thyroid gland cancer called papillary thyroid carcinoma.

About this article

This article was written by medical doctors in conjunction with patient advisers. It was designed to help patients read and understand their pathology reports. If you have any questions about this article, please contact us.

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