P-110 A CASE OF PAPILLARY THYROID MICROCARCINOMA PRESENTING BONE METASTASIS

Abstract Introduction Papillary thyroid microcarcinoma (PTMC), characterized as papillary thyroid carcinoma measuring ≤1 cm in diameter, typically has an excellent prognosis with elevated survival rates. Regional cervical lymph node metastases occur in 17.1% of cases, although bone metastases are exceptionally uncommon. We present a case of papillary thyroid microcarcinoma discovered following the detection of bone metastases. Clinical Case A 66-year-old male patient presented to the orthopedics clinic with complaints of left hip pain. Imaging revealed an 84 × 48 mm malignant lesion extending from the posterior left acetabulum to the left ischium. Tru-cut biopsy demonstrated metastasis from well-differentiated thyroid carcinoma, and the patient was referred to our endocrinology clinic. The patient’s medical history included essential hypertension and hemorrhagic cerebrovascular event 10 years earlier. No family history of thyroid cancer was noted. On physical examination, a nodule of approximately 2 cm was palpated at the thyroid isthmus. Thyroid function tests were within the euthyroid range. Neck ultrasonography revealed a 4 mm nodule in the mid-portion of the right thyroid lobe and a hypoechoic nodule measuring 18 mm in the isthmus, without pathological lymph nodes. Total thyroidectomy was recommended. For the acetabular lesion, five sessions of radiotherapy were administered. Postoperative pathology demonstrated multifocal (three foci) papillary microcarcinoma of the follicular subtype (infiltrative) located in the left lobe. The tumors, measuring 0.7 cm, 0.7 cm, and 0.2 cm, were encapsulated and exhibited capsular invasion. There was no angioinvasion or lymphatic invasion. Surgical margins were intact. The tumor was suspected to have arisen in a background of follicular adenoma. BRAF mutation was negative; TERT mutation could not be assessed. Levothyroxine suppression therapy was initiated (target TSH