Histologic changes in Graves' thyroid gland after 131I therapy for hyperthyroidism.

Area of Science:

• Endocrinology
• Pathology
• Nuclear Medicine

Background:

• Graves' disease is a common cause of hyperthyroidism.
• Radioactive iodine (131I) therapy is a standard treatment for hyperthyroidism.
• Long-term effects of 131I therapy on thyroid pathology are not fully understood.

Purpose of the Study:

• To investigate the long-term pathological changes in thyroid glands after 131I therapy for Graves' disease.
• To assess the clinical and microscopic findings in patients 3 to 29 years post-irradiation.
• To evaluate the potential for misdiagnosis of these changes.

Main Methods:

• Retrospective analysis of 13 thyroid glands from patients treated with 131I for Graves' disease.
• Clinical assessment of thyroid status (hypothyroid, euthyroid, hyperthyroid) and presence of nodules.
• Microscopic examination including routine histology and immunohistochemical staining (TG, T4, EGF, CEA).
• DNA ploidy analysis.

Main Results:

• Patients presented with palpable thyroid nodules years after 131I therapy.
• Microscopic findings included adenomatous nodules, cystic changes, oxyphilic cell changes with nuclear atypism, and chronic thyroiditis.
• Immunohistochemistry was largely negative for specific markers, and DNA ploidy was diploid in most cases.
• One papillary microcarcinoma was found, unrelated to irradiation.

Conclusions:

• Pathological changes after 131I therapy for Graves' disease are non-specific.
• Marked nuclear atypism in oxyphilic cells necessitates differentiation from adenomatous goiter and thyroid carcinoma.
• Careful pathological evaluation is crucial for accurate diagnosis in patients with a history of 131I therapy.