Risk factors for metastasis of papillary thyroid carcinoma to neck lymph nodes in preoperative N0 tumor status

Abstract

Damage to the lymph nodes of the neck by metastases of papillary thyroid carcinoma (PTC), in the vast majority of cases, begins with the lymphatic collector of the central part (VI and VII lymph drainage zones). At the same time, patients with primary N0 tumor status (based on physical examination, preoperative imaging, and examination during surgery) may have «latent» micrometastases in the lymph nodes of this location, which is important for stratifying the risk of lateral and distant metastases, as well as postoperative relapses. The aim is to analyze the frequency of PTC metastasis, in particular to the lymph nodes of the
central compartment, depending on a number of possible risk factors for metastasis. Material and methods. Retrospective cohort study of clinical data of 566 patients in whom preoperative examination did not reveal evident signs of metastases. The frequency of regional metastasis was estimated by the percentage in the cohort of patients with PTC categories N1a+N1b+N1ab (total), as well as separately for each category. Results. It has been established that the frequency of PTC metastasis to the lymph nodes of the neck of men is higher than that of women. This most significantly (by 2.2 times), concerns the frequency of metastasis to the lymph nodes of VI or VII lymph drainage zones (pretracheal, paratracheal or prelaryngeal/Delphian, upper mediastinal), as well as the lateral lymph nodes of the neck (zones I, II, III, IV or V, retropharyngeal lymph nodes) were classified as N1ab category tumor. The risk of metastases is sharply reduced in sick women (but not in men) aged 31-40 years due to its decrease in N1a and N1ab category tumors. In both women and in men, the frequency of metastases is increased for tumors larger than 1 cm (N1b and N1ab categories) compared to those for microcarcinoma, as well as for intra-organ metastasis – intrathyroidal and, especially sharply, with invasion of tumor cells into the tumor capsule (N1a and N1ab categories). With extrathyroidal invasion, the incidence of metastasis in women (but not in men) continues to increase; the lateral lymph nodes are affected separately (N1b category). Multifocality it isn’t asignificant risk factor, and the presence of chronic autoimmune thyroiditis protects the lymph nodes of all locations from increased PTC metastasis. Conclusions. Assessment of  high-risk factors for the existence of «latent» metastatic lymph nodes in the central lymph drainage compartment of the neck, some of which can be assessed only after surgical intervention and pathomorphological examinations, is important in predicting relapses and prolongation of the disease. The existence of a significant number of «latent» micrometastases in the central lymph nodes indicates the need to perform their prophylactic
dissection in patients with preoperative N0 tumor status.