The role of micro-RNA 155 and 429 in diagnosis of thyroid tumors

The thyroid gland, located in the anterior neck, is essential for controlling metabolism, growth, and calcium homeostasis through the secretion of triiodothyronine (T3), thyroxine (T4), and calcitonin. Cancer of the thyroid represents the most prevalent endocrine malignancy, with papillary thyroid carcinoma accounting for over 80% of cases. Its incidence has significantly increased globally, particularly among women, due to factors including estrogen receptor involvement and improved diagnostic techniques. The recent WHO Classification of Endocrine and Neuroendocrine Tumors (5th edition) has refined the categorization of thyroid neoplasms based on molecular profiles and biological behavior, distinguishing benign, low-risk, and malignant follicular cell–derived tumors.Diagnosis of thyroid nodules typically involves clinical examination, thyroid function tests, ultrasound, and fine-needle aspiration cytology (FNA), while molecular biomarkers have emerged as powerful tools to enhance diagnostic accuracy and guide treatment strategies. Among non-coding RNAs, microRNAs (miRNAs) have gained attention for their regulatory roles in tumorigenesis, acting as oncogenes (oncomiRs) or tumor suppressors. Dysregulated miRNA expression causes cancer initiation, progression, and therapeutic resistance. miR-155 functions as an oncomiR, promoting cell proliferation and metastasis in thyroid and other cancers, while miR-429, a member of the miR-200 family, exhibits tumor-suppressive properties by inhibiting proliferation, invasion, and epithelial–mesenchymal transition.Evidence suggests that circulating miRNAs, particularly miR-155 and miR-429, hold promise as less invasive biomarkers for early detection, therapeutic monitoring of thyroid cancer, and prognosis. Future clinical applications may incorporate these miRNAs alongside conventional diagnostic approaches to improve patient outcomes.