Goiter, Thyroid Nodules, and Selected Neoplastic Patterns

A goiter is an enlarged thyroid; the name does not specify functional status. Goiter can occur in hypothyroid, hyperthyroid, or euthyroid states, and thyroid size does not correlate with thyroid function.

Generalized thyroid enlargement is a diffuse goiter, whereas an irregular or lumpy enlargement is a nodular goiter. Prolonged stimulation by TSH or a TSH-like factor can produce diffuse enlargement; over time, focal hyperplasia, necrosis, and hemorrhage can produce nodules.

A multinodular goiter is an enlarged thyroid with multiple nodules. It is usually nontoxic and euthyroid. The tissue contains colloid nodules of varying sizes and may also show calcification, hemorrhage, cystic degeneration, and fibrosis.

Thyroid nodules can be described by iodine trapping. A hot nodule traps iodine and is hyperfunctioning; a cold nodule does not. The allowlist describes hot nodules as benign and identifies a solitary cold nodule as a presentation of thyroid cancer.

Radioiodine imaging separates diffuse from focal autonomy. Graves disease shows evenly increased uptake throughout an enlarged gland. A toxic adenoma shows one local area of increased uptake with suppression elsewhere. Toxic multinodular goiter shows multiple areas of high and low uptake.

A thyroid adenoma is a benign solitary growth. Most are nonfunctional and cold, although autonomous hormone production can rarely make an adenoma hot. Follicular architecture is common, and the absence of capsular or vascular invasion distinguishes adenoma from follicular carcinoma.

Papillary carcinoma can show branching papillae with fibrovascular cores and psammoma bodies. The cited source also describes lymphatic spread. A cold solitary thyroid nodule is compatible with this malignant pattern, whereas a hot autonomous nodule favors toxic adenoma.

Follicular carcinoma resembles thyroid follicles and spreads hematogenously. Medullary carcinoma has amyloid on light microscopy, with apple-green birefringence after Congo red staining. These tissue clues classify a cold malignant nodule rather than a hormone-secreting hot adenoma.