GOITER - The Solitary Thyroid Nodule
Thyroid nodules occur in approximately 5 per cent of the population. A nodule is a focal area of gland enlargement. It can be caused by a number of factors, but solitary nodules are predominantly adenomatous and benign (Table 68-6). Since a small percentage are carcinomatous, a practical clinical approach must be pursued to detect these patients. A number of factors from the clinical history, examination, and specific evaluations are helpful in the differentiation of benign from malignant lesions (Table 68-7). These relate to patient age and sex and whether the nodule is single or part of a multinodular gland. A young man presenting with a single dominant nodule associated with hoarseness and lymph node enlargement has a high possibility of malignancy. Any individual who presents with a nodule and a past history of head-neck irradiation should be referred for thyroidectomy, as these lesions are predominantly malignant (~ 30 per cent).
The traditional approach is to perform a RAIU study initially to determine the functional status of the nodule. Scanning with 123I will demonstrate no accumulation (”cold nodule”), equal isotope trapping (”warm nodule”), or greater accumulation (”hot nodule”) when compared with the rest of the gland. Warm and hot nodules are overwhelmingly benign (99.8 per cent). Cold nodules are also predominantly benign (90 per cent). Patients with hot nodules may be hyperthyroid. These can be treated effectively with 131I therapy. Generally, however, they are not currently hyperthyroid, but they should be followed carefully, since approximately 30 per cent will eventually become hyperthyroid.
Most solitary nodules are “cold” (80 per cent). A definitive pathological diagnosis can be made in most of these subjects (80 per cent) by cyto-logical examination of a tissue specimen obtained by fine needle aspiration biopsy (FNA). In fact, most centers now perform FNA as the initial procedure. Benign lesions (75 per cent) such as benign thyroid nodules, multinodular goiter, and thyroiditis can be identified by the expert cytol-ogist. In addition, malignant lesions (5 per cent), such as papillary, anaplastic, and medullary carcinoma, can be specifically diagnosed. Follicular neoplasms (20 per cent), however, cannot be identified.as benign or malignant by this technique , and require examination of tissue specimens obtained by surgical excision. Despite the lack of sensitivity in the analysis of the follicular neo-’ plasm, FNA has proved to be a powerful diagnostic procedure in the evaluation of the thyroid nodule. The ability to make a definitive diagnosis through the application of this safe and simple technique has markedly reduced the need for diagnostic thyroid surgery. The therapy for a malignant nodule is considered in the section on thyroid carcinoma. Benign lesions are treated with T4 suppression therapy. Regression of the nodule may occur during a six-month course. Generally, longstanding nodules remain stable and do not progress. Should the nodule increase in size, it should be reevaluated and the appropriate therapy instituted.