Endocrine Abstracts

JOINT1950

Introduction: Papillary thyroid carcinoma (PTC), a subtype of differentiated thyroid carcinoma (DTC), is classified as papillary thyroid microcarcinoma (PTMC) when ≤1.0 cm. Distant metastases from PTMC are rare (0-2.8 %). Therefore, long-term assessment of patients receiving surgical treatment and radioactive iodine is essential, since approximately 50% of DTC patients with distant metastases are classified as radioiodine-refractory, influencing survival rates.

Case: A 51-year-old female presented with a two-year history of a right neck mass.

Neck ultrasound: Revealed a 0.9×0.6 cm lymph node with hyperechoic foci in the right level IV region.

Thyroid ultrasound: Identified a ~0.2 cm hypoechoic nodule with ill-defined margins near the capsule on the right lobe (EU-TIRADS 5).

Fine-needle aspiration biopsy: Confirmed metastasis of PTC.

Laboratory tests: TSH, FT4, FT3, anti-TPO, anti-Tg within reference ranges.

Surgery: Subsequently, in April 2024 the patient underwent thyroidectomy and lymphadenectomy. TSH suppression (<0.1 mIU/l) is maintained with L-thyroxine 175 mg/day.

Microscopic examination: A 0.3 cm poorly defined, non-encapsulated tumor with papillae and pleomorphic cells, not invading the capsule; the pathological neck lymph node was not identified or removed.

SPECT/CT: Whole-body SPECT/CT revealed lung foci and I-131 uptake in the thyroid lodge and a level VI lymph node. The patient was diagnosed with stage II PTC, pT1aN1M1, and bilateral lung metastasis.

Radioiodine therapy: A cumulative dose of 6,1 GBq of iodine-I31 treatment was administered. SPECT/CT showed resolved lung I-131 uptake and faint residual thyroid and lymph node uptake. On November 2024, laboratory results: TSH at 0.01 mIU/l (n.r. 0.4-3.6), thyroglobulin at 0.2 mg/l, and anti-TG at 6.1 kU/l (n.r. <13.6). On January, 2025, thyroglobulin was <0.2 mg/l, and anti-TG was <1.3 kU/l. Concurrently, whole-body scintigraphy was performed. Laboratory and scintigraphy results proved an excellent biochemical and radiological response.

Discussion: A 0.3 cm PTMC, histologically benign in nature, caused metastases in the cervical lymph nodes and lungs. Nevertheless, I-131 therapy was effective in treating patient’s condition. Although active surveillance is becoming the standard approach for PTMC, the potential for metastasis in some cases highlights the need for prompt surgical intervention.