Thyroid cancer is often manifested by thyroid nodules. Therefore, it is important to distinguish the benignity and malignancy of nodules when nodular goiter is encountered in clinical practice. The most common diseases that cause goiter are as follows: 1. Simple goiter The most common cause of goiter is simple goiter. The history of the disease is usually long and often grows gradually and unknowingly, and is discovered incidentally due to physical examination. Nodules develop as the gland proliferates and compensates, with most presenting as multinodular goiter and a few as a single nodule. Most nodules are gelatinous, with some forming cysts due to hemorrhage and necrosis; in long-standing cases, there may be more fibrosis or calcification, or even ossification in some areas. Due to the nature of the nodule pathology, they vary in size, firmness, and shape. Thyroid bleeding often has a history of sudden swelling and pain with cyst-like masses in the gland; those with gelatinous nodules have a harder texture; those with calcification and ossification have a hard texture. 2. Subacute thyroiditis The size of the nodule depends on the extent of the lesion and is often hard in texture. There is a typical medical history, including rapid onset, fever, sore throat, and significant pain and pressure in the thyroid area. In the acute phase, the thyroid uptake rate decreases and the image is mostly “cold nodules” with elevated serum T3 and T4, which are “segregated” and contribute to the diagnosis. Chronic lymphocytic thyroiditis: a symmetric diffuse goiter without nodules; sometimes due to asymmetric enlargement and surface lobing, it may resemble a nodule, hard as rubber, without pressure pain. The disease is slow in onset and has a chronic progression, but it can occur at the same time as thyroid cancer and is not easily distinguishable clinically. Anti-thyroglobulin and anti-thyroid peroxidase antibody titers are often elevated. Invasive fibrous thyroiditis: the nodules are hard and fixed with adhesions to adjacent tissues outside the gland. The clinical manifestations resemble thyroid cancer, but the local lymph nodes are not large and the uptake I rate is normal or low. 3.Thyroid adenoma is caused by thyroid adenoma or multiple gelatinous nodules. Single or multiple, may coexist with goiter or appear alone. Adenomas are generally round or oval in shape, mostly harder in texture than the surrounding thyroid tissue, and are not painful to pressure. The scan shows normal, increased, or decreased I uptake; thyroid images are “warm nodules”, “hot nodules”, and “cold nodules”. The thyroid uptake rate may be normal or high. The tumor develops slowly and is mostly asymptomatic clinically, but some patients develop hyperfunctional symptoms. 4.Thyroid cysts contain blood or clear liquid, clearly demarcated from the surrounding thyroid tissue, and can be quite hard.