Anatomical relationship between localization of thyroid cancers and metastatic lymph node regions

Objective: The incidence of thyroid cancers has been increasing in the past 30 years. In the treatment of thyroid cancers, total thyroidectomy/lobectomy and in the presence of metastasis to the lymph nodes, compartment-oriented lymph node dissection in the cervical region are performed. In recent years, radical surgical approaches have been replaced by more selective and minimal surgical approaches. In the literatüre, there are studies aiming to predict metastatic lymph node regions according to tumor localizations to determine the surgical scope. In this study, our aim is to investigate the relationship between the localization of tumors in the lobe and metastatic lymph node regions. Materials and Methods: In our study, 304 patients were selected for investigating the risk of metastasis from the 2053 patients that were referred to Cukurova University Nuclear Medicine Department between 2007-2019 for radioactive iodine treatment. 103 of all patients with regional lymph node metastasis at the time of diagnosis were also determined and the relationship between tumor localization and metastasis foci were investigated in that group. Tumor localizations were seperated into subgroups as upper half, lower half in both lobes and isthmus. In addition, another group which consists 11 patients with medullary thyroid cancer and applied for PET / CT imaging between 2005-2019 and whose sufficient information could be obtained was created. In these three groups, the number and rates of the pathological and demographic features of the patients, the features associated with metastasis and the relationship between tumor localizations and metastatic lymph nodes were examined by using the IBM SPSS Statistical Version 20.0 package program. Results: Our first study group consisting of 304 patients and investigating the risk of metastasis, 246 (80.9 %) were women and 58 (19.1 %) were men and the mean age was 45.5 ± 12.8. Papillary thyroid cancer was the most common pathological type. A statistically significant relationship was found between extrathyroidal extension with lymphovascular invasion and metastasis to regional lymph nodes (p<0.001). In addition, the mean of tumor diameters were statistically different metastatical and non- metastatical tumors in the left lobe (1.20 and 1.90; p=0.013). In our second group consisting of 103 patients with lymph node metastasis, 69 (67 %) were women and 34 (33 %) were men, and the mean age was 39.46 ± 15.5. All patients had papillary thyroid cancer. A significant relationship was found between tumors located in the right half of the upper lobe with right Level III (p=0.015) and lateral lymph nodes (p=0.047). In addition, when the relationship between tumor localization on the lobe base and lymph node regions was examined regardless of multicentricity, a statistically significant relationship was found between tumors location in the right and left lobes with the presence of lymph node metastasis in both lateral cervical regions (p<0.001). Statistical evaluation could not be performed in medullary thyroid cancer group because adequate data of patients for statistical analysis could not be obtained. Conclusion: Regional lymph node metastasis is a common and significant clinical condition for both differentiated thyroid cancer and medullary thyroid cancers. In our study, no significant correlation was found between tumor localizations and metastatic lymph nodes at both levels I, V and VI. Our findings support the idea of performing a more selective lymph node dissection in the surgical approach, These findings also showed that the risk of metastasis to both lateral regions is similar for a tumor located in any lobe. Therefore, evaluation of regional lymph nodes with imaging methods during diagnosis is critical.