Answer: Diffuse hyperplasia (Graves’ disease)

Histology: Grossly the thyroid was symmetrically enlarged, weighing 120 grams. Low power histologic examination shows an accentuation of the normal lobularity of the thyroid but without focal discrete masses. There is hyperplasia of the follicles, and scalloping of the colloid where it abuts the follicular epithelium. A particularly striking architectural feature is the presence of well formed papillary structures. These papillae are relatively simple in that they lack complex tertiary branching. They are lined by columnar cells with enlarged nuclei. The nuclei are uniformly aligned along the base of the cells, and they do not exhibit any significant crowding and dyspolarity.

Discussion: Graves’ disease is an autosomal disorder characterized by circulating thyroid stimulating antibodies that induce a hyperactive state of the thyroid. Grossly and microscopically, it is seen as a diffuse hyperplasia of the thyroid parenchyma. Grave’s disease serves to remind that the morphologic features commonly used to diagnose papillary thyroid carcinoma are not always specific for malignancy. Papillary architecture, as one example, is sometimes encountered in lesions that are entirely benign such as nodular hyperplasia and particularly Grave’s disease. Although these papillae may be quite florid, they lack the overall complexity and tertiary branching seen in the papillae of papillary carcinoma. The benign nature of these papillae can usually be recognized by their broad base; their short and stubby size; their lack of nuclear atypia; and their “centripetal” pattern – the tips of these benign papillae all point to the center of the follicles.

The concurrence of cytologic atypia is seen when patients have undergone preoperative treatment with radioactive iodine. The atypia generally takes the form of scattered epithelial cells with enlarged, misshapen and hyperchromatic nuclei. This patient was treated with propranolol. These peripheral beta blockers do not incite cellular atypia.