Although it is rare to obtain pathological examination of thyroid glands in the early phase of development of multinodular goiters, such glands should show areas of hyperplasia with considerable variation in follicle size. The more typical specimen coming to pathologists is the goiter that has developed a nodular consistency. Such goiters characteristically present a variegated appearance, with the normal homogeneous parenchymal structure deformed by the presence of nodules (Fig. 17-5a,b, below). The nodules may vary considerably in size (from a few millimeters to several centimeters); in outline (from sharp encapsulation in adenomas to poorly defined margination for ordinary nodules); and in architecture (from the solid follicular adenomas to the gelatinous, colloid-rich nodules or degenerative cystic structures). The graphic term Puddingstone goiter has been applied. Frequently the nodules have degenerated and a cyst has formed, with evidence of old or recent hemorrhage, and the cyst wall may have become calcified. Often there is extensive fibrosis, and calcium may also be deposited in these septae. Scattered between the nodules are areas of normal thyroid tissue, and often-focal areas of lymphocytic infiltration. Radioautography shows a variegated appearance, with RAI localized sometimes in the adenomas and sometimes in the paranodular tissue. Occasionally, most of the radioactivity is confined to a few nodules that seem to dominate the metabolic activity of the gland.

Figure 5. (A) Cross section of multinodular goiter. (B) Gross radioautograph of the thyroid in part a. Observe the variation in 131I uptake in different areas.

If careful sections are made of numerous areas, 4-17% of these glands removed at surgery will be found to harbor microscopic papillary arcinoma43,50-52 The variable incidence can most likely be attributed to the different criteria used by the pathologists and the basis of selection of the patients for operation by their physicians. These factors are discussed below.