UC Irvine

INTRODUCTION: Thyroid cancer is the most common endocrine tumor in humans. Follicular adenoma/carcinoma is the second most common subtype. Multiple histological patterns have been identified. Follicular adenoma with bizarre nuclei is one of the patterns associated with p53 mutation and has an unclear clinical prognosis. CASE REPORT: A 74-year-old female presented with incidental findings of elevated TSH levels and normal thyroid markers. Ultrasound was performed and revealed multiple bilateral thyroid nodules measuring up to 1.9 cm. Fine needle aspiration was performed, and cytology showed one Bethesda category 5 nodule. Total thyroidectomy with neck dissection was performed, and the pathology showed follicular adenoma with bizarre nuclei. Based on the results of immunohistochemistry, the neoplastic cells exhibited staining for wild-type p53 and low levels of the proliferation index Ki-67. CONCLUSIONS: We report a rare case of thyroid follicular adenoma with bizarre nuclei. In contrast to previous reports of this tumor, our patient showed a p53 wild-type pattern using immunohistochemistry. More studies are needed to better understand the etiology and clinical prognosis of this tumor.