Answer: Hashimoto’s thyroiditis

Histology: The lesion is characterized by lymphocytic infiltration of the thyroid stroma, and oxyphilic change in the follicular epithelium. In addition, numerous germinal centers are found throughout the gland. The Hurthle cells are seen in follicles and also in solid cell nests that have features suggesting squamous metaplasia. The follicular infiltrate is composed predominately of lymphocytes with admixed plasma cells. In some cases giant cells may be found as well.

Discussion: It is probable that the thyroid diseases traditionally known as lymphocytic thyroiditis and Hashimoto’s thyroiditis represent different manifestations of an immune-mediated inflammatory process known clinically as “autoimmune thyroiditis”. These diseases are characterized functionally by the production of autoantibodies that alter thyroid function. Morphologically, the common denominator is the presence of prominent lymphocytic infiltration in the thyroid gland, usually associated with germinal center formation. Hashimoto’s Thyroiditis is predominately a disease of middle-aged women. Clinically, the lesion presents as diffuse, but firm, thyroid enlargement, sometimes accompanied by signs of local compression. The early stage of the disease may be accompanied by mild hyperthyroidism; later, hypothyroidism supervenes. At surgery, the thyroid gland is easily separated from other structures, a feature that clinically helps to separate Hashimoto’s Disease from the stony, hard infiltrative lesion known as Riedel’s Thyroiditis.

Our case represents the typical presentation of Hashimoto’s Thyroiditis. There is a fibrous variant of this disease. With dense hyaline fibrosis and atrophy of the follicular epithelium. The danger in the fibrous variant of Hashimoto’s Disease is confusion with carcinoma. Hashimoto’s Thyroiditis is typically a diffuse disorder, but there are cases in which prominent nodularity is evident. The epithelial cells in these nodules appear hyperplastic. The term “Nodular Hashimoto’s Thyroiditis” is applied to these cases. The nodular form of Hashimoto’s Thyroiditis can produce another problem in differential diagnosis when one of the nodules appears separate from the main body of the thyroid. In that instance, the differential diagnosis will include metastatic thyroid carcinoma. Integration of the clinical findings, and the findings in the remainder of the gland will resolve the issue.

Complications of Hashimoto’s Thyroiditis include malignant lymphoma, papillary carcinoma and Hurthle cell neoplasms.