Endocrine Abstracts

JOINT3562

Background: Studies have suggested that papillary thyroid carcinomas incidentally detected by nuclear medicine imaging techniques may have a worse prognosis compared to those identified by other methods. However, it remains unclear whether this observation applies to papillary thyroid microcarcinomas (PTMCs).

Aim: To compare the prognostic differences among PTMCs detected by nuclear medicine imaging (e.g., 18F-FDG PET, technesium-99m-MIBI), incidental PTMCs, and non-incidental PTMCs using pathological tumor characteristics.

Methods: Patients diagnosed with PTMC in Hacettepe University School of Medicine between 2008 and 2020 were categorized into three groups: (1) PTMCs detected by nuclear medicine imaging methods (n = 24), (2) incidental PTMCs (n = 251), and (3) non-incidental PTMCs (n = 132). Tumor pathology characteristics, including multifocality, extrathyroidal extension, vascular invasion, and lymph node involvement were analyzed. Logistic regression analysis was performed to assess the association between detection method and tumor aggressiveness, adjusting for potential confounders such as age at diagnosis.

Results: Patients with PTMCs detected by nuclear medicine imaging were significantly older at diagnosis (54.7±11.7 years) compared to incidental PTMCs (51.0±11.4 years) and non-incidental PTMCs (47.1±11.8 years) (P = 0.001). Tumor size was also significantly different among groups (P < 0.0001), with nuclear medicine-detected PTMCs (4.8±2.5 mm) and non-incidental PTMCs (5.3±2.3 mm) being larger than incidentally detected PTMCs (3.4±2.4 mm). Logistic regression analysis showed that PTMCs detected by nuclear medicine imaging were significantly more likely to be bilobar compared to incidentally detected PTMCs (OR: 4.59, 95% CI: 1.55-14.58, P = 0.006). The rate of cervical lymph node metastasis was markedly higher in PTMCs detected by nuclear medicine imaging compared to both incidentally detected PTMCs (OR: 41.13, 95% CI: 9.33-191.20, P < 0.0001) and non-incidental PTMCs (OR: 3.82, 95% CI: 1.16-12.58, P = 0.027). However, there were no significant differences among the groups in terms of extrathyroidal extension or vascular invasion.

Conclusions: Although nuclear medicine-detected PTMCs were larger in size and associated with a significantly higher rate of cervical lymph node metastasis and bilobar involvement compared to incidental PTMCs, other aggressive pathological features did not significantly differ. These findings suggest that PTMCs identified by nuclear medicine imaging may have distinct biological behavior, warranting further investigation to determine their true prognostic implications.