Thyroid Nodules Located in the Lower Pole Have a Higher Risk of Malignancy than Located in the Isthmus: A Single-Center Experience

Characteristics and risk factors of cervical lymph node metastasis in cN0 papillary thyroid microcarcinoma of the isthmus

The surgical resection range of papillary thyroid microcarcinoma of the isthmus (PTMCI) is controversial, and the guidelines do not fully guide the central lymph node dissection (CLND).We retrospectively studied the comparison of PTMCI (Group A, n = 65 cases) and non-PTMCI (Group B, n = 80 cases). Based on whether central lymph node metastasis (CLNM) was further detected, they were further divided into the PTMCI with CLNM (group C, n = 42 cases), the PTMCI without CLNM (group D, n = 23 cases), the non-PTMCI with CLNM (group E, n = 45 cases), the non-PTMCI without CLNM (group F, n = 35 cases). All patients underwent total thyroidectomy and CLND. The CLNM pathological examination was divided into right recurrent laryngeal nerve superficial lymph nodes (Right VI a), right recurrent laryngeal nerve deep lymph nodes (Right VI b), left VI area lymph nodes (Left VI), prelaryngeal lymph node, and pretracheal lymph node. The extent of lymph node metastasis and risk factors of PTMCI were analyzed by univariate and multivariate analysis. The ROC curve was used to calculate the maximum diameter of the tumor and the Youden index was calculated to analyze the impact of diameter on the risk factors for CLNM in PTMCI. To construct a prediction model of transfer risk of high risk factors by Nomogram, there were significant differences in prelaryngeal lymph nodes (p = 0.034) and pretracheal lymph nodes ( n = 0.035) between group A and group B, and the risk factors of lymph node metastasis were tumor invasion (p = 0.003), multifocality (p = 0.001), and the maximum tumor diameter≧6.5 mm. PTMCI is more prone to metastasis of pretracheal lymph nodes and prelaryngeal lymph nodes, and the presence of tumor invasion, multifocality, and tumor diameter≧6.5 mm are high risk factors for metastasis in PTMCI. According to the prediction model, with all risk factors the risk of cervical lymph node metastasis is up to 90%.

Introducing a Pole Concept for Nodule Growth in the Thyroid Gland: Taller-than-Wide Shape, Frequency, Location and Risk of Malignancy of Thyroid Nodules in an Area with Iodine Deficiency

Purpose: (i) To examine the criterion taller-than-wide (TTW) for the sonographic assessment of thyroid nodules in areas of iodine deficiency in terms of frequency, anatomical distribution within the thyroid gland and risk of malignancy. (ii) To develop a model for nodule growth in the thyroid gland. Methods: German multicenter study consisting of two parts. In the prospective part, thyroid nodules were sonographically measured in all three dimensions, location within the thyroid gland and contact to a protrusion-like formation (horn) in the dorsal position of thyroid gland was noted. In addition, further sonographic features such as the composition, echogenity, margins and calcifications were investigated. All nodules from the prospective part were assessed for malignancy as part of clinical routine at the decision of the treating physician adhering to institutionally based algorithms. In the retrospective part, only nodules with fine needle aspiration and/or histology were included. The risk of malignancy in TTW nodules was determined by correlating them with cyotological and histological results. Results: Prospective part: out of 441 consecutively evaluated thyroid nodules, 6 were found to be malignant (1.4%, 95% CI 0.6–2.7%). Among the 74 TTW nodules (17%), 1 was malignant (1%, 95% CI 0–4%). TTW nodules were more often located in the dorsal half of the thyroid than non-TTW nodules (factor 2.3, p = 0.01, 95% CI 2.1–2.5) and more often located in close proximity to a horn than non-TTW nodules (factor 3.0, p = 0.01, 95% CI 2.4–3.8). Retrospective part: out of 1315 histologically and/or cytologically confirmed thyroid nodules, 163 TTW nodules were retrieved and retrospectively analyzed. A TTW nodule was 1.7 times more often benign when it was dorsal (95% CI 1.1–2.5) and 2.5 times more often benign when it was associated with a horn (95% CI 1.2–5.3). The overall probability of malignancy for TTW nodules was 38% (95% CI 30–46%) in this highly preselected patient group. Conclusion: TTW nodules are common in iodine deficient areas. They are often located in the dorsal half of the thyroid gland and are frequently associated with a dorsal protrusion-like formation (horn) of the thyroid. Obviously, the shape of benign nodules follows distinct anatomical preconditions within the thyroid gland. The frequency of TTW nodules and their predominant benignity can be explained by a pole concept of goiter growth. The difference between the low malignancy risk of TTW nodules found on a prospective basis and the high risk found retrospectively may be the result of a positive preselection in the latter.