A perimenopausal woman presents with increasing swallowing difficulty and fatigue. Physical examination reveals that her thyroid is enlarged (palpable goiter). Laboratory examination of her serum reveals T4 of 4.9 mg/dL, free T4 of 2.5 ng/dL, and TSH of 5.5 mIU/mL. No thyroidstimulating immunoglobulins are identified in the serum, but antimicrosomal antibodies are present. Which one of the listed histologic findings, if present in a thyroid biopsy from this individual, would be most consistent with a diagnosis of Hashimoto's thyroiditis?

Four types of thyroiditis may be associated with hypothyroidism. Hashimoto's thyroiditis, one of the autoimmune thyroid diseases, is associated with the HLA-B8 haplotype and high titers of circulating autoantibodies, including antimicrosomal, antithyroglobulin, and anti-TSH receptor antibodies. This abnormality is not uncommon in the United States. Histologically, there is infiltration of the thyroid stroma by an intense lymphoplasmacytic infiltrate, with the formation of lymphoid follicles and germinal centers. This produces destruction and atrophy of the follicles and transforms the thyroid follicular cells into acidophilic cells. There are many different names for these cells, including oxyphilic cells, oncocytes, Huhle cells, and Askanazy cells. Not uncommonly, patients develop hypothyroidism as a result of follicle disruption, and the manifestations consist of fatigue, myxedema, cold intolerance, hair coarsening, and constipation. Rarely, cases of Hashimoto's thyroiditis may develop hypehyroidism (Hashitoxicosis), while the combination of Hashimoto's disease, pernicious anemia, and type I diabetes mellitus is called Schmidt's syndrome. This is one type of multiglandular syndrome. Although subacute thyroiditis and Riedel's thyroiditis may have similar symptoms to Hashimoto's thyroiditis, biopsy findings in these disorders are distinctly different. Subacute (de Quervain's, granulomatous, or giant cell) thyroiditis is a self-limited viral infection of the thyroid. It typically follows an upper respiratory tract infection. Patients develop the acute onset of fever and painful thyroid enlargement, and may develop a transient hypothyroidism. Histologically there is destruction of the follicles with a granulomatous reaction and multinucleated giant cells that surround fragments of colloid. One-half of patients with Riedel's thyroiditis are hypothyroid, but, in contrast to the other types of thyroiditis, microscopic examination reveals dense fibrosis of the thyroid gland, often extending into extrathyroidal soft tissue. This fibrosis produces a rock-hard enlarged thyroid gland that may produce the feeling of suffocation. This combination of signs and symptoms may be mistaken clinically for a malignant process. Additionally, these patients may develop similar fibrosis in the mediastinum or retroperitoneum. Subacute lymphocytic thyroiditis is also a self-limited, painless enlargement of the thyroid that is associated with hypothyroidism, but that lacks antithyroid antibodies or lymphoid germinal centers within the thyroid Hashimoto's thyroiditis Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition