The standard approach to diagnose thyroid tumors involves fine needle aspiration biopsy (FNAB) for cytological evaluation. However, inconclusive cases often necessitate histopathological examination of tissue specimens. Core needle biopsy presents a non-surgical alternative, enabling the acquisition of diagnostic material and, in some cases, preventing unnecessary surgical interventions. This study aims to assess the significance of core needle biopsy in diagnosing suspicious nodular thyroid lesions with inconclusive FNA results.

Between 2019 and 2022, core needle biopsies were performed on 51 patients with suspected malignant thyroid tumors and inconclusive FNAB results. Tissue specimens underwent comprehensive histopathological, immunohistochemical, and molecular examinations.

Out of 51 cases, 48 yielded appropriate tissue specimens, with three requiring a repeat biopsy. Diagnoses included 20 cases of primary epithelial cancers (anaplastic, low-differentiated, medullary, oncocytic, papillary or follicular). Other diagnoses included pleomorphic sarcoma, high-grade sarcoma, B-cell lymphoma, NUT midline carcinoma, chemodectoma, low-differentiated neuroendocrine tumor, histiocytoma, malignant peripheral nerve sheath tumor and cancer metastases from various origins. Complications were rare, with 94.1% of biopsies being uncomplicated. Hematomas at the biopsy site occurred in two patients, and one case showed anaplastic cancer cell implantation in the biopsy needle canal.

Core needle biopsy is a secure procedure for obtaining adequate tissue samples for histopathological and genetical examination of thyroid nodules. It serves as a viable option when FNAB results are inconclusive and can guide appropriate treatment, potentially averting unnecessary surgical resections.