Hyalinizing trabecular tumor of the thyroid gland: A case report and a brief review of the literature

Thyroid hyalinizing trabecular tumors (HTTs) are rare benign tumors that often mimic other malignant tumors, posing a diagnostic challenge. We report a case of a 39-year-old female with no significant past medical history who presented to her family physician for a routine annual visit. On thyroid palpation, a firm, non-tender nodule was felt in the right lobe. The patient denied awareness of the nodule or experiencing any symptoms, such as weight loss or gain, heat or cold intolerance, or neck pain. Thyroid laboratory studies were unremarkable, and thyroid peroxidase and thyroglobulin antibody tests were negative. Thyroid ultrasound revealed a solid, hypoechoic mass measuring 2.1 x 1.8 x 1.6 cm in the right lobe. There was heterogeneous echogenicity with multiple scattered microcalcifications, increased vascularity, and irregular margins, which raised suspicion for malignancy. Fine needle aspiration (FNA) was performed, and the cells were found to be aggregated in clusters, some forming trabeculae, with nuclear grooves and occasional intranuclear pseudoinclusions, which suggested papillary thyroid carcinoma (PTC). FNA results were challenging to differentiate from malignancy, given the absence of typical architectural patterns for PTC. A diagnostic hemithyroidectomy was performed. Histopathological examination and immunohistochemistry (IH) studies showed tumor cells positive for MIB-1, thyroglobulin (Tg), and TTF-1. Final diagnosis of thyroid HTT was made. Considering it is a benign neoplasm, and the patient already had a right hemithyroidectomy, there was no indication for further surgery. The patient’s remaining thyroid function was normal, and she did not require any hormone replacement. Three years after initial diagnosis, the patient reported no symptoms or signs of recurrence. This case details a rare benign tumor that closely mimics malignancy, highlighting the importance of a thorough diagnostic workup to ensure accurate diagnosis