ThyrOID NODUle – revISIT

Thyroid nodules are common and are being more commonly identified with improvement in imaging modalities. Because thyroid nodules are frequently found incidentally during routine physical examination or imaging performed for another reason, physicians from a diverse range of specialties encounter thyroid nodules. Clinical decision making depends on proper evaluation of the thyroid nodule. Diagnosis and treatment selection require a risk stratification by history, physical examination, and ancillary tests. Nodules causing airway compression or those at high risk for carcinoma should prompt evaluation for surgical treatment. In nodules larger than 1 cm, fine-needle aspiration biopsy is central to the evaluation as it is accurate, low risk, and cost effective. Subcentimeter nodules, often found incidentally on imaging obtained for another purpose, can usually be evaluated by ultrasonography. Other laboratory and imaging evaluations have specific and more limited roles. The treatment modalities range from observation to surgical resection in a small percentage of thyroid nodules. A number of non-surgical modalities are being explored with variable success rates. Thyroid nodules are common. They are discovered by palpation in 3% to 7%, by Ultrasonography in 20% to 76%, and by autopsy in approximately 50% . Prevalence increases linearly with age, exposure to ionizing radiation, and iodine deficiency. Thyroid nodules are more common in women than in men. In the ThyrOID NODUle – revISIT rakesh sahay, V sri Nagesh Framingham population study, follow-up indicated new nodules in 1.3% in 15 years, calculated as an annual incidence of 100 cases per 100,000 persons per year. The clinical importance of thyroid nodules, besides the infrequent local compressive symptoms or thyroid dysfunction, is primarily the possibility of thyroid cancer, which occurs in about 5% of all thyroid nodules regardless of their size. Clinical evaluation begins with a detailed patient history and careful thyroid palpation. (Table 1 lists the various causes of thyroid nodules) An inquiry should be made about family history of benign or malignant thyroid disease. The malignancy rate for nodules in young persons is 2-fold higher than in adult patients. Previous disease or treatments concerning the neck (history of childhood head/neck radiation), rapidity of onset, and rate of growth of the neck swelling should be enquired. Appearance of a new mass, progressive nodule growth, a firm or hard solitary or dominant nodule, or the presence of adjacent cervical adenopathy, symptoms of invasion such as airway compression, hoarseness and dysphagia are suspicious for malignancy and should prompt further evaluation. A thorough physical examination of the head and neck should be conducted. The thyroid gland and nodules within it move with swallowing while masses external to the thyroid do not. The size of the nodule, its consistency (firm, cystic or rubbery) should be noted as firmer the nodule the greater is the chance for malignancy. Fixation of the nodule also suggests cellular invasion and malignancy. Pemburton’s sign should be evaluated to assess the degree of substernal extension, careful palpation for cervical lymph nodes, assessment of mobility of vocal cords are other important points to be noted in the physical examination. Table 2 lists the clinical features indicating a higher risk for malignancy in a thyroid nodule UltrAsoNogrAphy (Us): Thyroid ultrasonography is emerging as a very useful noninvasive tool in the evaluation of thyroid nodules. When examined by ultrasound, thyroid nodules are commonly detected with a prevalence of 40% to 50% in the general population. The ultrasound table 1 : common causes of thyroid nodules Benign Colloid nodule hashimoto thyroiditis Simple or hemorrhagic cyst Follicular adenoma Subacute thyroiditis Malignant Primary Follicular cell-derived carcinoma: PTC, follicular thyroid carcinoma, anaplastic thyroid carcinoma C-cell–derived carcinoma: MTC Thyroid lymphoma Secondary Medicine Update 2010  Vol. 20 450 features that are consistently associated with malignancy are: i) hypoechogenicity, ii) Increased vascularity, iii) Microcalcifications, iv) Irregular margins, v) Absence of a halo. The vascularity of a thyroid nodule is demonstrated with color flow Doppler (CFD) or power Doppler (PD) imaging. Nodule vascularity is categorized as absent, perinodular, or intranodular. Increased intranodular flow is associated with malignancy and has good interobserver variability. Microcalcifications image as echogenic foci smaller than 2 mm and are associated with malignancy. Microcalcifications are thought to represent aggregates of psammoma bodies characteristic of many papillary cancers, and are rarely found in benign nodules or follicular neoplastic lesions. Coarse calcifications may be associated with malignancy when they appear with microcalcifications or in the center of a hypoechoic nodule. Peripheral calcifications can be seen in malignant nodules, sometimes with interruption of the circumferential calcific rim that suggests malignant invasion of thyroid parenchyma. Irregular margins are seen with invasion of a malignant nodule into the surrounding thyroid parenchyma, e.g., an unencapsulated papillary cancer. The irregular margin is less commonly observed with encapsulated follicular or hurthle cell cancers A halo is described as a thin hypoechoic rim that surrounds a nodule and is thought to represent compression of the extranodular blood vessels as a benign nodule slowly grows. An invasive malignancy, such as unencapsulated papillary cancer or medullary cancer,lacks a halo. however, follicular and hurthle cell adenomas and cancers are generally surrounded by a fibrous avascular capsule. This capsule images sonographically as a thick, irregular hypoechoic rim, which is now recognized as a more dangerous second type of halo. AdditioNAl soNogrAphic feAtUres 1. Shape of the nodule :A/T ratio greater than 1.0, indicating a spherical nodule this detected thyroid cancer with a sensitivity of 84% and a specificity of 82%. 2. extrathyroidal invasion may be occasionally seen when the tumor growth extends through either the anterior or posterior thyroid capsule, which normally appears as a bright white outline surrounding the thyroid. Some series have explored the association of combinations of features with cancer risk. In most series, as the specificity of a combination increases, the sensitivity decreases. Papillary thyroid cancers are more likely to be solid, hypoechoic, and lack a halo compared with follicular thyroid cancers. Follicular cancers most commonly have a halo (90%), which is irregular (60%) and are isoto hyperechoic. Therefore, it is critical to recognize that ultrasound does not replace FNA cytology, rather the two modalities are complementary