| Background: Papillary thyroid carcinoma(PTC)occurs most frequently in thyroid carcinoma,accounting for more than 80% of the morbidity of thyroid cancer.Papillary thyroid microcarcinoma(PTMC)refers to PTC with a maximum diameter of 1 cm or less than 1 cm.These years,The morbidity of PTC is increasing all the time,which is largely due to the increased incidence of PTMC.It is well known that most PTMC develop slowly and have a good prognosis,but there are still some patients with PTMC who have suffered from recurrence,distant metastasis or even death.So clinically,the treatment of PTMC patients has been controversial.From the recently proposed "close observation of low risk" to the "surgical treatment" which has been adhering to,there is no definite treatment plan.The choice of surgical scope is not uniform,In addition,there is no conclusion on whether preventive central lymph node dissection should be performed in PTMC patients with cN0 stage.Obviously,how to screen low-risk and high-risk PTMC patients is the key to formulate clinical treatment programs.At present,researches have demonstrated that lymph node metastasis(LNM)increases the danger of reappeared of PTMC patients,and the more lymphatic metastasis,the higher the risk of recrudescence.Besides,LNM is common,especially in central lymph node metastasis(CLNM).However,preoperative ultrasound and other examinations are difficult to detect them.In recent years,medical workers have carried out in-depth studies on the relationship between the clinicopathological characteristics of PTMC and CLNM.It has been confirmed that male,multiple lesions and extraglandular tissues by cancer cells are independent factors affecting the occurrence of CLNM in PTMC.Multiple lesions(referred to as multiple lesions)represent two or more PTMC lesions in the thyroid gland lobe.In addition,multifocal PTMC accounted for about 20% to 40% of PTMC.However,what is the intrinsic reason for the increase of CLNM caused by multiple cancers?If the number of cancer foci and total tumor diameter(TTD,refers to the sum of the maximum diameter of each lesion in multiple lesions)are used to represent multiple lesions,what is the relationship between them and CLNM?Currently,existing datas suggest that the more PTMC tumors are,the more likely CLNM is to occur.In addition,for PTMC,the risk of CLNM in patients with TTD > 1 cm was significantly higher than that in patients with TTD < 1 cm and single focus.In order to further explore the biological characteristics of multifocal PTMC,Some scholars even researched multifocal PTMC as a single subtype of PTMC;The data suggested that the incidence of thyroid capsule involvement by cancer cells,local recurrence of cancer and LNM was significantly higher in multifocal PTMC than that in single-focus PTMC,and that multifocal PTMC was more invasive and should adopt a similar intraoperative and post-operative management model as PTC.However,the research on multi-foci PTMC,In particular,the relationship between the number of cancer foci,the total diameter of tumors and CLNM,is still in its infancy,with limited research data and lack of evidence,more research is urgently needed.Objective: To further search the nexus with tumor number,overall diameter and CLNM of multifocal PTMC,to clarify the intrinsic correlation between multifocal PTMC and central lymph node metastasis,to accumulate evidence for the biological characteristics of multifocal PTMC,and to explore the treatment options for multifocal PTMC patients.Methods: The clinical and pathological data of 459 patients with PTMC confirmed by pathology after initial surgical treatment were included in this retrospective study.Through sample size estimation and equilibrium test,it shows that the sample size is sufficient to meet the statistical requirements,and the gender composition and age composition among groups are balanced and comparable.According to the number of different lesions,the patients were divided into single PTMC group,two PTMC tumors group and ≧ 3 PTMC tumors group,The differences of CLNM between different number of cancer lesions were compared.According to the total diameter of tumors,the patients were divided into single-focus PTMC group,multi-focus PTMC and TTD≦ 1 cm group,multi-focus PTMC and TTD > 1 cm group;among them,multiple lesions indicate that there are two or more PTMC lesions in thyroid gland lobe,and the sum of the maximum diameter of all lesions is TTD(total tumor diameter).The differences of CLNM between groups with different total diameter of tumors were compared.The clinicopathological characteristics of multi-focus PTMC and single-focus PTMC were compared.Results: Among the 459 PTMC patients,319(69.5%)were single focus PTMC patients,140(30.5%)were multi-focus PTMC patients,89(19.4%)were PTMC patients with 2 lesions and 51(11.1%)were PTMC patients with 3 or more than 3 lesions.64 cases(13.9%)were multifocal PTMC with TTD ≦ 1cm,and 76 cases(16.6%)were multifocal PTMC with TTD > 1cm.By comparison,positive rate of CLNM was different among different tumor number groups(P=0.001<0.05);furthermore,multiple comparisons of CLNM among different tumor number groups(at the test standard of α’= 0.0125)were conducted,and the statistical data showed that the positive rate of CLNM in two lesions PTMC was significantly higher than that in single PTMC(P = 0.001 < 0.0125).Similarly,the positive rate of CLNM in thyroid micropapillary carcinomas with three or more than three tumors was also significantly higher than that in single lesion(P < 0.0125).Moreover,compared with the two PTMC lesions,the positive rate of CLNM in lesions with≧3 PTMC tumors was also significantly higher(P=0.001 < 0.0125).Therefore,the higher the number of PTMC tumors,the higher the probability of CLNM.Similarly,CLNM was also different among groups with different total tumor diameters(P=0.001 < 0.05);further multiple comparisons of CLNM among groups with different TTD(at the test standard of α’= 0.0125)were conducted.The results showed that there was no difference in central lymph node metastasis between single-focus PTMC patients and multifocal PTMC patients with TTD ≦ 1cm(P=0.08>0.0125).However,the CLNM positive rate of multiple PTMC with TTD >1cm was significantly higher than that of single foci and multiple foci with TTD ≦1cm(P=0.001).In this study,the clinicopathological features were compared between multifocal PTMC and single PTMC.The sex composition of patients with multiple PTMC was different from that of patients with single PTMC(P=0.03 < 0.05),and most multiple PTMC patients were female.In terms of CLNM comparison,multifocal PTMC patients were also significantly higher than that of single-focus PTMC group(P=0.001).However,there was no difference in age composition,capsular invasion and extrathyroidal extension between multifocal PTMC patients and single PTMC patients(P > 0.05).Conclusion:Multiple foci are the main influencing factor of CLNM in thyroid micro papillary carcinoma,moreover,the more the tumor number,the higher the incidence of CLNM,for multifocal PTMC patients with TTD>1cm.,the lymph node metastasis rate of central region is significantly higher than that of PTMC patients with single focus and multifocal PTMC patients with TTD≦1cm.Therefore,multifocal PTMC is highly invasive and prone to central lymph node metastasis,total/near total thyroidectomy plus preventive central lymph node dissection(PCLND)is recommended.especially for PTMC patients with large number of cancer foci and TTD > 1 cm,Total/near-total thyroidectomy plus preventive central lymph node dissection is necessary. |
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