Abstract / Summary
The incidence of medullary thyroid microcarcinoma (MTMC) is increasing and represents a significant proportion of all medullary thyroid carcinoma (MTC) cases. However, there is a lack of research on how the tumor size and outcome of initially undiagnosed MTMCs evolve before surgery. A retrospective analysis of 75 MTMC cases at our center was performed. Among patients whose diagnosis and surgery had been delayed, 20 with assessable baseline imaging were analyzed for tumor growth during a preoperative observational period exceeding six months. The study aimed to evaluate this growth and to investigate the relationships between tumor size, invasive pathological features, and MTMC outcome. Among the 20 patients with delayed surgery, 75% (15/20; 95% CI 53.1–88.8%) showed sonographic evidence of MTMC nodule growth during a median observational period of 27 months. The final nodule volumes were significantly larger than the initial volumes ( p < 0.001). When patients were grouped by a 5 mm threshold, tumors > 5 mm showed higher preoperative calcitonin and CEA levels, a greater incidence of lymph node metastasis, more advanced TNM stage, and a lower rate of biochemical cure than tumors ≤ 5 mm (all p < 0.01). Correlation analysis showed that tumor size in MTMC was positively associated with preoperative calcitonin ( r = 0.357, p = 0.022) and CEA ( r = 0.428, p = 0.003) levels, lymph node metastasis ( r = 0.388, p = 0.001), TNM stage ( r = 0.416, p < 0.001), and worse outcome ( r = 0.330, p = 0.006). Most MTMCs enlarged when surgery was delayed, and larger tumor size was associated with worse outcomes. Although tumor size and observation time are linked in this setting, our findings indicate that MTMC should not be presumed to remain stable during an untreated interval. This supports prompt diagnosis and timely surgery once MTMC is suspected, although the clinical implications require confirmation in future studies. Not applicable.