September 16, 2025

Hyalinizing trabecular tumor: Sheep in the Wolf’s clothing! – A case report and review of the literature

Key Points

Diagnosis revealed a rare hyalinizing trabecular tumor following total thyroidectomy and lymph node dissection, which is often confused for papillary thyroid carcinoma.
Histopathology showed trabecular growth and hyalinization, indicating a marked distinction from medullary thyroid carcinoma.
Immunohistochemistry testing confirmed low Ki-67 index and absence of BRAF mutation, setting it apart from similar thyroid tumors.
Differentiation of this tumor is crucial for accurate management, emphasizing the need for careful histopathological evaluation.

Abstract

ABSTRACT Hyalinizing trabecular tumor (HTT) is a rare neoplasm of follicular origin. It is often mistaken for classic papillary thyroid carcinoma (PTC) or medullary thyroid carcinoma (MTC) due to overlapping cytological and architectural features. We report a 49-year-old woman presenting with a left-sided thyroid nodule of 6 months’ duration. Ultrasound had shown a solid hypoechoic TIRADS 3 lesion (29 mm × 14 mm), and FNAC was suggestive of Bethesda category V. Her thyroid-stimulating hormone was 4.04 μIU/ml. She underwent total thyroidectomy with bilateral lymph node dissection. After histopathology, it showed a classic trabecular growth pattern and prominent hyalinization. Immunohistochemistry revealed a low proliferation index (Ki-67-peripheral staining), absent BRAF mutation, and PAS-positive, Congo red-negative stroma-differentiating it from PTC and MTC. A diagnosis of a hyalinizing trabecular tumor of the thyroid was made.

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