According to Global Cancer Statistics, in 2020, 586,000 people fell ill with thyroid cancer, which made it possible to occupy the ninth place in the structure of malignant neoplasms. Papillary and follicular types of thyroid cancer are the most common and account for more than 90% of all cases. At the time of diagnosis, metastases in the neck lymph nodes are diagnosed in 30-80% of patients. Therapeutic neck dissections are indicated for these patients. However, the volume of surgical intervention required for patients with occult metastases in the lymph nodes of the neck is a subject of debate among many scientists.
The position of Western guidelines (NCCN and ESMO), is somewhat different from the Eastern one (JSTS and JAES). According to NCCN and ESMO recommendations, lymph node dissection is performed only in cases with clinically diagnosed metastases. On the other hand, the Japanese Society of Endocrine Surgeons recommends thyroidectomy and central neck dissection, as this volume of surgical intervention can reduce the risk of regional recurrences.
The dissertation is devoted to the actual problem of substantiation of the volume of lymphatic dissection in patients with highly differentiated forms of thyroid cancer and the study of biomineralization processes in lymph nodes of the neck. The following methods were used to analyze the research results: surgical treatment of patients, histological, histochemical, immunohistochemical, histomorphometric, physicochemical research methods, statistical method.
The study was conducted on two groups of patients, which were divided according to the applied diagnostic and treatment methods. The group А included 123 patients, and the group В - included 64 patients.
A 1% solution of toluidine blue was applied to patients of the group А to detect sentinel lymph nodes. Based on the results of sentinel lymph node biopsy and total thyroidectomy in combination with central and lateral neck dissection performed on all patients in the investigated group, it was possible to establish an identification rate, sensitivity, specificity, positive predictive value and negative predictive value, false positive and false negative rates of 1% toluidine blue solution. Total thyroidectomy and central neck dissection were performed for treating patients in the group В. Toluidine blue was not used, and a sentinel lymph node biopsy was not performed.
Among 123 patients of group A who underwent central and lateral neck dissection, metastases in the central compartment were found in 31 (25.2%) patients. In 35.5% of patients, metastases spread to the VI, and in 6.5% - to the VII level of lymph nodes of the neck of those who had metastasis in LN. Metastases in the lateral compartment were found in 24 (19.5%) patients. Among them, metastases in level III cervical lymph nodes were confirmed in 24 patients (100%) and level IV in 8 patients (33.3%), which is significantly higher compared to level V (4.2%). «Skip» metastases were found in 6 (4.9%) patients.
It was established that the frequency of complications in patients after total thyroidectomy + central neck dissection + lateral neck dissection was higher than total thyroidectomy + central neck dissection. Performing a lateral neck dissection is associated with an increased risk of wound exudation (seroma), lymphorrhea, and inflammation. Postoperative paresis of the vocal cords occurred with the same frequency in patients of both groups.
Metastases in the central lymphatic collector were detected in the case of tumor location in the lower third of the lobe of the thyroid gland (48.4%) and isthmus (60.0%). Metastases in the lateral lymphatic collector were detected in the case of the location of the tumor in the upper third of the lobe of the thyroid gland (24.5%). The malignant process mainly spreads to the III and IV levels of lymph nodes of the neck. According to our research, in most cases, primary tumors localized in the upper third of the lobe of the gland had a higher frequency of «skip» metastases compared to tumors of other localizations. "Skip" metastases were located mainly in the III and IV levels of lymph nodes of the neck.
An important part of the work was the study of biomineralization processes. The prevalence of the biomineralization process in the lymph nodes of patients with highly differentiated forms of thyroid cancer was established. All cases were determined to be associated with the papillary form of thyroid cancer. We used scanning electron microscopy for samples with signs of pathological biomineralization.
Based on the results of the biopsy of sentinel lymph nodes and data on the localization of the primary tumor, the choice of the volume of lymphatic dissection in patients with highly differentiated forms of thyroid cancer is justified. The importance of biomineralization in regional lymph nodes was investigated, and recommendations were given for interpreting the biopsy results of sentinel lymph nodes.
