Impact of microscopic extrathyroidal extension on differentiated thyroid cancer post-surgical risk of recurrence: a retrospective analysis

Impact of location and size of minimal extrathyroidal extension on lymph node metastasis in papillary thyroid cancer: a retrospective analysis

Background

The 8th edition of the American Joint Committee on Cancer (AJCC)'s T-stage for differentiated thyroid cancer (DTC) removes minimal extrathyroidal extension (mETE), while ignoring the risk of mETE would lead to overtreatment or inadequate treatment. The aim of this study was to investigate the impact of location and size of mETE on lymph node metastasis in papillary thyroid cancer (PTC).

Methods

A retrospective analysis of 267 patients who underwent unilateral radical surgery for PTC was conducted. According to the postoperative pathology, they were divided into mETE group (121 patients) and non-mETE group (146 patients). The number of lymph nodes dissected and the number of lymph nodes metastasized were compared between the two groups. The linear regression analysis and the receiver operating characteristic (ROC) curves were performed to evaluate the impact of the locations and sizes on lymph node metastasis.

Results

There was no significant difference in the number of lymph node dissected between the mETE group and the non-mETE group. The tumor located at the upper part and the size <1.0 cm in mETE group showed a higher number of lymph node metastasis (0.78±0.88 vs. 0.25±0.45, P=0.03). Meanwhile, in the mETE group, the number of patients with lymph node metastasis was higher than that in the non-mETE group. Further subgroup analysis revealed that for PTC patients with tumors at the upper part and size <1.0 cm, the number of those with lymph node metastasis in the mETE group was also greater than that in the non-mETE group. Furthermore, the Spearman correlation analysis showed a positive correlation between tumors located at the upper part with a size <1.0 cm and lymph node metastasis rate (R=0.647, P=0.004). Additionally, if the upper part tumor was within 1 cm, the tumor's size was able to identify the lymph node metastasis, with the optimal cut-off point of 0.45 cm (Youden index =0.650).

Conclusions

When tumors combine with mETE, the probability of lymph node metastasis increases in tumors located at the upper part with a size <1.0 cm. Especially, when the upper part tumor is within 1 cm, the tumors of size ≥0.45 cm are more likely to have lymph node metastasis.

Microscopic extrathyroidal extension does not affect the prognosis of patients with papillary thyroid carcinoma: A propensity score matching analysis

Background

Extrathyroidal extension (ETE) in papillary thyroid carcinoma (PTC) can be divided into two categories based on different degrees of invasion: microscopic ETE (micro-ETE) and macroscopic ETE (macro-ETE). At present, there is a consensus that macro-ETE significantly affects PTC prognosis, while the prognostic significance of micro-ETE remains controversial.

Methods

The clinicopathological and follow-up data for PTC patients who underwent surgical treatment at the Hangzhou First People's Hospital between 2015 and 2018 were retrospectively analyzed. According to the degree of ETE, patients were divided into three groups: non-ETE, micro-ETE and macro-ETE. Cox regression analysis was performed to evaluate the effect of ETE on recurrence-free survival (RFS). The propensity score matching (PSM) method was used to reduce the interference of confounding factors, and Kaplan-Meier curves were utilized to compare the RFS.

Results

Both micro- and macro-ETE were associated with some aggressive tumor features, including tumor size, multifocality, and lymph node metastasis. Univariate and multivariate Cox regression analyses showed that macro-ETE was an independent risk factor for recurrence, while micro-ETE was not associated with recurrence. The K-M curves showed that RFS for micro-ETE and non-ETE were not statistically different before and after PSM, while RFS for macro-ETE was significantly shorter than that for non-ETE.

Conclusion

The presence of micro-ETE in PTC did not affect prognosis of patients, suggesting that its treatment should be consistent with the treatment for intrathyroidal tumors. The surgical method and the necessity for radioiodine therapy should be carefully evaluated to reduce overtreatment.