This book looks into the complex realm of thyroid gland lesions, including both neoplastic and non-neoplastic categories. Non-neoplastic lesions, such as thyroglossal duct cysts, inflammatory diseases, and hyperplastic syndromes, are thoroughly described. Granulomatous thyroiditis, a self-limiting inflammatory illness that primarily affects females, with clinical symptoms similar to viral infections. Fibrous thyroiditis, including Riedel's thyroiditis, is distinguished by fibrosis that extends beyond the thyroid gland, giving it a woody feel. The most common thyroiditis, Hashimoto's thyroiditis, frequently results in goiter and hypothyroidism. Graves disease, an autoimmune illness, also produces excessive thyroid hormone production. The book highlights the relevance of histopathology and immunohistochemistry in detecting thyroid lesions, including indicators such as Leu M1, HBME-1, and galactin-3. Overall, this study provides a thorough examination of thyroid gland abnormalities, including histological features and clinical consequences.