Fig.20.11A ).Olderlesionsoftenshowareasoffibrosis,hemorrhage,calcification,andcysticchange.Themicroscopicappearanceincludescolloid-richfollicleslinedbyflattened,inactiveepitheliumandareasoffollicularepithelialhypertrophyandhyperplasia,accompaniedbytheregressivechangesjustnoted(see
Fig.20.11B
Fig.20.11Multinodulargoiter.(A)Grossmorphologicappearance.Thecoarselynodularglandcontainsareasoffibrosisandcysticchange.(B)Photomicrographofaspecimenfromahyperplasticnodule,withcompressedresidualthyroidparenchymaontheperiphery.Thehyperplasticfolliclescontainabundantpink“colloid”withintheirlumina.Notetheabsenceofaprominentcapsule,afeaturedistinguishingsuchlesionsfromneoplasmsofthethyroid.(B, Courtesy of Dr.William Westra,Department of Pathology,Johns Hopkins University,Baltimore,Maryland.) http://ebooksmedicine.net
The dominant clinical features of goiter are those caused by the mass effects of the enlarged gland. In addition to the obvious cosmetic problem of a large neck mass, goiters also may cause airway obstruction, dysphagia, and compression of large vessels in the neck and upper thorax (so-called “superior vena cava syndrome”).
Multinodular goiters typically are hormonally silent, but a minority (approximately 10% over 10 years) manifest with thyrotoxicosis secondary to the development of autonomous nodules that produce thyroid hormone independent of TSH stimulation. This condition, known as toxic multinodular goiter or Plummer syndrome, is not accompanied by the infiltrative ophthalmopathy and dermopathy of Graves disease–associated thyrotoxicosis. The incidence of malignancy in long-standing multinodular goiters is low (<5%) but not zero, and concern for malignancy arises with goiters that demonstrate sudden changes in size or associated symptoms (e.g., hoarseness).
Thyroid tumors range from circumscribed, benign adenomas to highly aggressive, anaplastic carcinomas. From a clinical standpoint, the possibility of a tumor is of major concern in patients who present with thyroid nodules. Fortunately, the overwhelming majority of solitary nodules of the thyroid prove to be either benign adenomas or localized, non-neoplastic conditions (e.g., a dominant nodule in multinodular goiter, simple cysts, or foci of thyroiditis). Carcinomas of the thyroid, by contrast, are uncommon, accounting for less than 1% of solitary thyroid nodules. Several clinical criteria provide a clue to the nature of a given thyroid nodule:
Solitary nodules, in general, are more likely to be neoplastic than are multiple nodules.
Nodules in very young (<20 years) or very old (>70 years) individuals are more likely to be neoplastic.
Nodules in males are more likely to be neoplastic than are those in females.
A history of radiation exposure is associated with an increased incidence of thyroid malignancy.
Nodules that take up radioactive iodine in imaging studies (hot nodules) are more likely to be benign.
Such associations, however, are of little significance in the evaluation of a given patient, in whom the timely recognition of a malignancy may be lifesaving. Ultimately, morphologic evaluation of a thyroid nodule by fine-needle aspiration, combined with the histologic study of surgically resected thyroid tissue, provide the most definitive information about the nature of the nodule.