The Value Of Ultrasonography In The Diagnosis Of Follicular Variant Of Papillary Thyroid Carcinoma And Central Lymph Node Metastasis

BackgroundHigh-frequency ultrasound has become the first choice for the examination of thyroid and cervical lymph nodes with convenient operation,radiation-free,good repeatability and high accuracy.In recent years,with the application of high-frequency ultrasound,the detection rate of thyroid nodules larger than 5mm has risen up to 12.8%.Thyroid cancer accounts for 5-15%of thyroid nodules,ranking first in malignant tumors of the head and neck.Diffentiated thyroid carcinoma accounts for 90-95%of all thyroid cancer,which mainly includes papillary carcinoma,follicular carcinoma and eosinophilic tumor.Papillary thyroid carcinoma(PTC)is the most common differentiated thyroid carcinoma,and it can be divided into several subtypes:classical variant,follicular variant,tall cell variant and so on.Follicular variant of papillary thyroid carcinoma(FVPTC)is secondary to classical papillary thyroid carcinoma(CPTC),accounting for 22.5%of all papillary thyroid carcinomas.The histological feature of FVPTC is completely or almost entirely composed of follicles,which makes the imaging findings,clinicopathological features and biological behavior of FVPTC overlap with some benign thyroid tumors.It's still a great challenge for preoperative diagnosis of FVPTC.Compared to CPTC,FVPTC is less invasive with better prognosis.However,cervical lymph node metastasis was found in 22.8%of FVPTC patients,and lymph node metastasis is an important predictor for prognosis of FVPTC.So it is of great value to define the preoperative lymph node metastasis of FVPTC for clinical treatment.In this study,we analyzed the sonographic and clinicopathological features of FVPTC and CPTC,and divided the FVPTC patients into two groups according to the central lymph node metastasis status.Multivariate logistic analysis was used to explore risk factors of central lymph node metastasis in FVPTC patients.We aimed to provide basis for preoperative diagnosis of follicular variant of papillary thyroid carcinoma and central lymph node metastasis.Part 1 Analysis of ultrasonographic and clinicopathologic features in follicular variant of papillary thyroid carcinomaObjective:To explore the ultrasonographic features and clinicopathological features of FVPTC in comparison with CPTC.Methods:From August 2017 to September 2019,a total of 323 cases of pathologically proved PTC in Henan Cancer Hospital were enrolled in the study.There were 115 patients with FVPTC and 208 patients with CPTC.All patients underwent preoperative BRAFV600E gene mutation examination.The above-mentioned cases were examined by preoperative high frequency ultrasound of thyroid and cervical lymph nodes and retained the sonographic data.Two senior ultrasound doctors unknown to pathological results evaluated the ultrasonic features of each nodule independently.When inconsistent,consensus was reached after consultation.The factors of FVPTC and CPTC were compared as follows:ultrasonographic features(composition,echogenicity,shape,margin,echogenic foci);ACR TI-RADS scores and clinicopathological features(age,sex,number of nodules,maximum diameter,BRAFV600E gene mutation,extrathyroid invasion,Hashimoto thyroiditis).P<0.05 was considered of statistically difference.Results:Postoperative pathological results showed that there were 323 cases of pathologically proved PTC,including 115(35.60%)cases of FVPTC,208(64.40%)cases of CPTC.The characteristics with statistical differences of FVPTC and CPTC were as follows:margin(P=0.016),echogenicity(P<0.001),echogenic foci(P=0.012),ACR TI-RADS scores(P<0.001),average age(P=0.001),>45years old(P=0.002),BRAFV600E gene mutation(P<0.001),extrathyroidal invasion(P=0.006).Conclusion:Compared to CPTC,FVPTC is more likely to show smooth margin,hyperechoic or isoechoic internal echo,less punctate echogenic foci,lower ACR TI-RADS scores,older patients,lower BRAFV600E gene mutation rate and less extrathyroid invasion.Part 2 Analysis of risk factors of central lymph node metastasis in follicular variant of papillary thyroid carcinomaObjective:To investigate the ultrasonographic and clinicopathological features associated with central lymph node metastasis(CLNM)in follicular variant of papillary thyroid carcinoma(FVPTC).Methods:A total of 102 FVPTC nodules in 102 patients who underwent thyroid surgery in our hospital from August 2017 to July 2019 were enrolled in the study.According to the postoperative pathological results,the patients were divided into central lymph node metastasis positive group and negative group.Univariate analysis was used to compare the differences in ultrasound and clinicopathological features between two groups.The significant features in univariate analysis were incorporated into multiple binary logistic regression to explore risk factors of central lymph node metastasis in FVPTC.Results:By univariate analysis,Margin(P=0.004),echogenic foci(P=0.046),gender(P=0.007),maximum diameter(P=0.001),extrathyroid invasion(P=0.013)were associated with central lymph node metastasis in FVPTC.Multivariate binary logistic regression analysis showed that the rough margin(P=0.002),maximum diameter>lcm(P=0.003),extrathyroid invasion(P=0.027)were independent risk factors for central lymph node metastasis in FVPTC.Conclusion:Rough margin,maximum diameter>1cm,and the extrathyroid invasion are the independent risk factors of central lymph node metastasis in FVPTC.