Low-Risk Papillary Thyroid Carcinoma Recurring as a Single Brain Metastasis: A Case Report and Literature Review

Background: Brain metastases from papillary thyroid carcinoma are infrequent occurring in 0.15% to 1.3% of patients, and they are generally accompanied by synchronous metastases in other sites and in isolation are even less frequent;the information about their management is limited and it has been based mainly on retrospective studies, experiences, case reports, and management guidelines of brain metastasis of other cancers. Aim: We report this case with the objective of describing how unpredictable the behavior of thyroid cancer can be despite being classified as low risk of recurrence. Case Presentation: A female patient with a diagnosis of papillary thyroid carcinoma classified as low risk who after more than a year of surveillance and without alterations in laboratory and imaging studies, developed a single brain metastasis susceptible to treatment with radioactive iodine (RAI) therapy. Conclusion: This case emphasizes the importance of a close follow-up of patients and not to minimize any symptom, no matter how simple it may seem, since cancer has no rules in its evolution.

Childhood Papillary Thyroid Carcinoma: A Case Report

Background: Thyroid cancer is a rare disease yet the most common endocrine malignancy in pediatrics. Unlike adult patients, children with thyroid nodules typically don’t complain of pain, soreness, or difficulty swallowing. Additionally, using the recommended therapy for adults to treat paediatrics is not appropriate. There is an unmet need for updated unique guidelines for the management of papillary thyroid carcinoma (PTC) in paediatrics and adolescents. Case Report: A 12-year-old girl had an atypical presentation of metastatic PTC in lymph nodes. She was treated initially with hemi-thyroidectomy, followed by total thyroidectomy. A multidisciplinary team followed her up till successful results were found. Conclusion: Due to the difference in pathophysiology between thyroid tumors in children and adults, a unique approach to PTC management is to be implemented. Further trials are required for a better understanding of risk factors, the likelihood of recurrence, and the long-term side effects of the chosen management plan.

Studies on surgical methods for sporadic micromedullary thyroid carcinoma

Background:To observe the changes in serum calcitonin levels after application of different surgical methods for primary medullary thyroid microcarcinoma(MTMC)and explore a more reasonable surgical method.Methods:A retrospective analysis of 36 patients with MTMC,16 in group A and 20 in group B,was performed.In group A,tumors were single and confined to the thyroid lobe,and thyroid lobectomy with isthmusectomy was performed.In group B,tumors were in the isthmus or invaded the thyroid gland,or there were multiple foci in bilateral lobes,and patients with primary foci underwent total thyroidectomy.The median follow-up time was 3.6 years.Clinical and pathological characteristics and changes in serum calcitonin(CTn)and carcinoembryonic antigen levels after the surgery were compared between the 2 groups.Results:The difference in the biochemical cure rate after surgery was statistically significant between patients with preoperative serum calcitonin levels<150 pg/mL and≥150 pg/mL(P<0.01).No significant differences in the biochemical cure rates and serum calcitonin levels were noted at different time points after surgery between group A and group B(P>0.05).One recurrence and metastasis were observed in each group after surgery.Conclusions:After performing different surgical methods for the primary foci of MTMC,the changes in serum calcitonin and carcinoembryonic antigen levels are similar.Especially for patients with single foci confined to the thyroid lobe without lateral cervical lymph node metastasis and with serum calcitonin levels<150 pg/mL,the unilateral thyroid lobectomy with isthmectomy can achieve the same therapeutic effect and biochemical cure rate as total thyroidectomy.

Role of prophylactic central neck lymph node dissection for papillary thyroid carcinoma in the era of de-escalation

Thyroid cancer is the most common endocrine malignancy.While there has been no appreciable increase in the observed mortality of well-differentiated thyroid cancer,there has been an overall rise in its incidence worldwide over the last few decades.Patients with papillary thyroid carcinoma(PTC)and clinical evidence of central(cN1)and/or lateral lymph node metastases require total thyroidectomy plus central and/or lateral neck dissection as the initial surgical treatment.Nodal status in PTC patients plays a crucial role in the prognostic evaluation of the recurrence risk.The 2015 guidelines of the American Thyroid Association(ATA)have more accurately determined the indications for therapeutic central and lateral lymph node dissection.However,prophylactic central neck lymph node dissection(pCND)in negative lymph node(cN0)PTC patients is controversial,as the 2009 ATA guidelines recommended that CND“should be considered”routinely in patients who underwent total thyroidectomy for PTC.Although the current guidelines show clear indications for therapeutic CND,the role of pCND in cN0 patients with PTC is still debated.In small solitary papillary carcinoma(T1,T2),pCND is not recommended unless there are high-risk prediction factors for recurrence and diffuse nodal spread(extrathyroid extension,mutation in the BRAF gene).pCND can be considered in cN0 disease with advanced primary tumors(T3 or T4)or clinical lateral neck disease(cN1b)or for staging and treatment planning purposes.The role of the preoperative evaluation is fundamental to minimizing the possible detrimental effect of overtreatment of the types of patients who are associated with low disease-related morbidity and mortality.On the other hand,it determines the choice of appropriate treatment and determines if close monitoring of patients at a higher risk is needed.Thus,pCND is currently recommended for T3 and T4 tumors but not for T1 and T2 tumors without high-risk prediction factors of recurrence.

Microwave ablation of solitary T1N0M0 papillary thyroid carcinoma:A case report

BACKGROUND The gold standard treatment for papillary thyroid carcinoma is total thyroidectomy and indications for microwave thermal ablation for primary thyroid cancers have not yet been clearly established However,some patients refuse surgery and others have no indication for it,for example patients under palliative care as in this case,or cannot undergo surgery,based on their comorbidities.These indications are described in the most recent Korean,North American and European guidelines.Laser ablation,radiofrequency ablation,and microwave ablation are similarly safe and effective,so the choice should be based on the specific competences and resources of the pertaining centers.These indications are Percutaneous minimally-invasive techniques;they can be useful to stop disease progression and as an alternative to surgery in patients with contraindication or who refuse surgery.We present a case of a thyroid papillary carcinoma with 17 mm effectively treated with microwave thermal ablation and without recurrence after one year of follow up.CASE SUMMARY The authors present a case of a 71-years-old patient with a left lobe papillary thyroid carcinoma with 13 mm×17 mm×13 mm,with no indication for thyroid surgery given the context of another cancer in palliative treatment.Microwave thermoablation was performed on December 2021.Four months later he repeated computed tomography(CT)scan,which showed that the tumor had disappeared.Six months after ablation he underwent a positron emission tomography/CT-fluorodeoxyglucose scan,which didn’t show any evidence of hypermetabolic tumor lesions.CONCLUSION This case shows microwave thermoablation can be a safe and effective alternative to surgery in patients with no conditions to undergo surgery or when they refuse it.By treating the tumor,with this minimally invasive technique,we are stopping its growth and avoiding disease progression.

Effect of Hashimoto’s Thyroiditis on Efficacy of 131I Ablation Therapy in Intermediate- and High-Risk of Thyroid Papillary Carcinoma

Objective: The purpose of this study was to investigate the effect of Hashimoto’s thyroiditis on efficacy of 131I ablation in intermediate- and high-risk of thyroid papillary carcinoma patients. The findings will help to develop a personalized treatment plan for patients with thyroid papillary carcinoma complicated with Hashimoto’s thyroiditis. Material and Methods: From January 2016 to December 2020, patients who were diagnosed with intermediate- and high-risk PTC with lymph node metastasis were analyzed retrospectively, excluding patients with incomplete clinical data, distant metastasis, positive TGAb, TSH Results: A total of 525 patients (166 males and 359 females) were included in the study, including 368 patients in ER group (70.1%) and 157 patients in NER group (29.9%). Eleven factors including combining Hashimoto’s thyroiditis, pre-ablative Tg levels, sex, tumor diameter, extraglandular invasion, multifocal, bilateral lesions, central lymph node metastasis, lateral lymph node metastasis, lymph node metastasis rate, thyroglobulin were statistically different between ER group and NER group with significance at P Conclusion: Hashimoto’s thyroiditis, Ps-Tg level and lateral lymph node metastasis are potential predictors for short-term efficacy of 131I treatment in intermediate- and high-risk thyroid papillary carcinoma. Hashimoto’s thyroiditis, high Ps-Tg level and increased number of lateral lymph node metastasis reduce the efficacy of 131I therapy in patients with intermediate and high risk thyroid papillary carcinoma.

Papillary thyroid carcinoma with nodular fasciitis-like stroma-an unusual variant with distinctive histopathology:A case report

BACKGROUND Papillary thyroid carcinoma(PTC)is regarded as a fairly common endocrine malignancy,which can be divided into different multiple variants due to wide morphologic differences.The majority of PTC variants have been reported,but PTC with nodular fasciitis-like stroma(NFS)is a rare pathological variant and has been infrequently reported in the relevant literature.This condition involves abundant reactive stromal components rich in spindle cells,which may account for 60%-80%of the tumor along with a typical papillary carcinoma.CASE SUMMARY A 44-year-old man presented with a 4-mo history of a palpable mass over the anterior aspect of the left neck,the tumor demonstrated gradual enlargement but was painless during the 4 mo prior to discovery.Thyroid function test results were normal.Physical examination showed an enormous and firm nodular mass in the left lobe of the thyroid gland extending to the level of the hyoid bone.Ultrasonography of the neck revealed a well-defined heterogeneous lesion measuring around 5.0 cm×4.0 cm with a hypoechoic complex nodule,decreased vascularity and speckles of microcalcification.The patient underwent left thyroidectomy with central compartment lymph node dissection.Final histopathological examination confirmed the diagnosis of PTC with extensive fibromatosis-like stroma combined with typical PTC.The patient was asymptomatic at the 3-mo follow-up.CONCLUSION PTC-NFS is a rare pathological variant and its diagnosis and prognosis may be similar to typical papillary carcinoma.

A Case of Papillary Thyroid Carcinoma Arising from Struma Ovarii and Extending into the Bladder

Ovarian goiter is a form of single tissue teratoma of the ovary, accounting for 2% - 3% of mature ovarian teratomas. Malignant transformation may occur in rare cases. Papillary thyroid-type carcinoma represents the most common type of malignant struma ovarii, followed by follicular carcinoma. Malignant struma ovarii is commonly seen in women in the fifth decade. The diagnosis is often made post-operatively after histological examination. Histology also helps assess tumor aggressiveness (mitoses, necrosis, poorly differentiated subtype, etc.). Given the rarity of these lesions, no therapeutic consensus or prognostic value had yet been formally established. We report herein, the case of a 76-year-old woman with a cystic tumor of the right ovary and a nodular lesion of the bladder. The clinical symptomatology is nonspecific, associating abdomino-pelvic pain and a right latero-uterine mass on abdominal palpation. After total hysterectomy with bilateral adnexectomy, the diagnosis of papillary carcinoma arising from struma ovarii and extending into the bladder was made. Through this observation, we suggest to discuss the anatomoclinical particularities of this rare pathological entity.

Papillary Thyroid Carcinoma and Pregnancy: What Impact on Prognosis?

Introduction: The impact of pregnancy on the prognosis of papillary thyroid carcinoma (PTC) has been debated for several decades;however, no definitive conclusions have been reached. The main objective of this study is to demonstrate the short-term influence of pregnancy on the evolution and prognosis of PTC. Materials and Methods: A prospective descriptive and analytical study was conducted in the Endocrinology and Diabetology Department at the Hassan II University Hospital in Fez, including patients followed for papillary thyroid carcinoma presenting with a pregnancy during the year 2019 and 2020. The follow-up of these patients was continued until 1 year postpartum. We studied the clinical, paraclinical and therapeutic factors that could influence the prognosis of the disease. Results: We included 26 patients. Our study showed a significant correlation between recurrence and the presence of unfavorable histological signs (p = 0.02) as well as the initial Tg level (0.01). However, pregnancy was not an influencing factor (p = 0.41). Conclusion: Pregnancy does not seem to be a factor aggravating the prognosis of differentiated thyroid cancers.

Predictive factors for central lymph node metastases in papillary thyroid microcarcinoma

Papillary thyroid microcarcinoma(PTMC)measures 1 cm or less in its longest dimension.The incidence of PTMC is increasing worldwide.Surgery is the primary treatment;however,prophylactic central lymph node dissection is controversial,and discrepancies between different guidelines have been noted.Routine prophylactic central lymph node dissection may result in hypoparathyroidism and recurrent laryngeal nerve injury in some patients without lymph node metastasis,while simple thyroidectomy may leave metastatic lymph nodes in high-risk patients.To selectively perform prophylactic lymph node dissections in high-risk patients,it is important to identify predictive factors for lymph node metastases in patients with PTMC.Several studies have reported on this,but their conclusions are not entirely consistent.Several clinicopathologic characteristics have been identified as risk factors for central lymph node metastases,and the most commonly reported factors include age,gender,tumor size and location,multifocality,bilaterality,extrathyroidal extension,and abnormal lymph node found using ultrasound.Here,we provide an overview of previous studies along with a favorable opinion on or against these factors,with the aim of increasing the understanding of this topic among the medical community.In addition,current opinions about prophylactic central lymph node dissection are reviewed and discussed.

Clinical and Sonographic Assessment of Cervical Lymph Node Metastasis in Papillary Thyroid Carcinoma

The purpose of this study was to assess the differences in clinical and sonographic features of papillary thyroid carcinoma（PTC） between cervical lymph node metastatic（CLNM） and nonmetastatic groups.Clinical data of PTC patients（414 patients with 624 malignant nodules） who underwent a preoperative ultrasonography and surgery between June 2010 and March 2015 at Renmin Hospital of Wuhan University were retrospectively analyzed.Clinical factors,preoperative ultrasound features and the final pathological findings were obtained.The differences in the sonographic features of PTC between the CLNM group and the non-CLNM group were analyzed.There were 187 CLNM and 227 non-CLNM patients.The median age at the diagnosis of this cohort was 45.4 years old（ranging from 18 to 77 years）.Ultrasonographic parameters that were significantly associated with CLNM [OR=2.569（1.502,4.393）,P〈0.001）] were as follows：the mulifocality of the nodules,size over 2 cm,the presence of microcalcifications,the distance ratio（DR） pattern showing the contact of the nodules with the thyroid capsule,and the extracapsular spread of the nodules.No significant differences in age,gender,thyroid stimulating hormone（TSH） levels and other ultrasonography parameters were found between the CLNM and the non-CLNM groups.Therefore,our results suggest that a larger size,microcalcifications,mulifocality,and the DR pattern showing the contact of the nodules with the thyroid capsule and extracapsular spread are significantly more indicative of CLNM in PTC.

The active surveillance management approach for patients with low risk papillary thyroid microcarcinomas: is China ready?

Due to exponential increases in incidences,low risk papillary thyroid microcarcinoma(PTMC)has become a clinical and social issue in recent years.An active surveillance(AS)management approach is an alternative to immediate surgery for patients with low risk PTMC.With decreased doubts about the safety and validity due to evidence from a large number of studies,the AS approach has become increasingly popular worldwide.However,Chinese thyroid surgeons still lag behind other countries in their knowledge of clinical practices and research related to AS.To promote the implementation of AS in China,thyroid surgeons should understand the implications,advantages,and disadvantages of management approaches for AS,and should also consider the willingness of Chinese patients,the impact on the medical billing system,and the enthusiasm of doctors.Thus,a management approach for AS based on the Chinese population should be developed to reduce the risk of disease progression and enhance patient adherence.Herein,we summarize the recent research achievements and deficiencies in AS approaches,and describe the initial experiences regarding AS in the Chinese population,in order to assist Chinese thyroid surgeons in preparing for AS management in the era of PTMC precision medicine.

Active surveillance as a management strategy for papillary thyroid microcarcinoma

Active surveillance(AS)can be considered as a treatment strategy for low risk papillary thyroid microcarcinoma(PTMC),with the absence of clinically apparent lymph nodes,extrathyroidal extensions,and distant metastasis.After reviewing the reports on AS of low risk PTMCs worldwide,we introduced AS,and discussed the selection criteria for active surveillance candidates based on different guidelines and the follow-up schedules.Moreover,the requirement of cytological diagnosis,progression evaluation methods,necessity of thyrotropin suppression,and medical costs were issues that both clinicians and patients considered.The usefulness of AS for low risk PTMC patients depended on accurate and confidential evaluation of patient risk.Clinicians may adopt measures like dynamic monitoring,risk stratification,and making personal follow-up schedules to minimize these potential risks.By appropriately selecting PTMC patients,AS can be an effective alternative treatment to immediate surgery.

Active surveillance in low risk papillary thyroid carcinoma

In recent decades,while the incidence of thyroid cancer has increased exponentially around the world,mortality has remained stable.The vast majority of this increase is attributable to the identification of intrathyroidal papillary microcarcinomas,which exhibit slow growth rates with indolent courses.A diagnosis of thyroid cancer based upon the presence of these small tumors could be considered as an overdiagnosis,as the majority of these tumors would not likely result in death if left untreated.Although surgical resection was the classical standard therapy for papillary microcarcinomas,active surveillance(AS)has emerged over the last three decades as an alternative approach that is aimed to recognize a minority group of patients who will clinically progress and would likely benefit from rescue surgery.Despite the encouraging results of AS,its implementation in clinical practice is strongly influenced by psychosocial factors.The aim of this review is to describe the epidemiology,clinical evolution,prognostic factors,and mortality of papillary thyroid microcarcinomas.We also summarize the AS strategy according to published evidence,characterize the criteria for selecting patients for AS according to risk factors and environmental characteristics,as well as analyze the current limitations for AS implementation.

Skull metastasis in papillary carcinoma of thyroid:A case report

Papillary thyroid carcinoma with metastasis to the skull is extremely rare.We report a case of unsuspected papillary thyroid carcinoma with skull metastasis.A 48-year-old female patient presenting with painless,pulsatile,progressively increasing swelling in the occipitoparietal region of the scalp approached for an X-ray of the skull.Ultrasound of palpable swelling in the neck revealed a heteroechoic lesion with increased vascularity.Foci of calcification were seen involving both lobes of the thyroid.Ultrasound of scalp showed a destructive mass in the skull with increased vascularity.Biopsy of thyroid lesions revealed branching papillae having a dense fibrovascular core covered by cuboidal epithelial cells with nuclei having a clear ground glass appearance.This case illustrates how isolated extensive skull metastasis can be found in papillary carcinoma patients without causing significant morbidity.Therefore,in the clinical course of thyroid papillary carcinoma,skull metastasis should be considered,and the patients should be meticulously investigated and followed up.

Skull metastasis revealing a papillary thyroid carcinoma

Although thyroid carcinoma is a relatively common form of malignancy,metastatic spread to the skull is rare.Here,we report a case of papillary thyroid carcinoma with frontal and parietal metastasis.A 61-year-old Chinese woman presented with a one year history of a growing mass on the center of the frontal and parietal bone,initially thought to be meningioma.Biopsy of the skull base mass after intracalvarium excision,indicated a tumor of thyroid origin.One month later the patient underwent a total thyroidectomy.Pathological examination confirmed a diagnosis of papillary thyroid carcinoma with frontal and parietal bone metastasis.Based on this experience,the key to successful management of the skull metastasis of thyroid carcinoma is prompt diagnosis and appropriate treatment.Skull metastasis should be considered at the outset of the clinical course of papillary thyroid cancer.To facilitate this,patients should be meticulously investigated by a multidisciplinary team to improve quality of life.

Clinicopathologic Characteristics of Differentiated Thyroid Carcinoma in Children and Adolescents

Objective: To investigate the clinicopathologic features of differentiated thyroid carcinoma in children and adolescents. Methods: The clinical data of 7 children and adolescents with differentiated thyroid carcinoma were retrospectively analyzed, and the clinicopathologic features of differentiated thyroid carcinoma were analyzed by gender, tumor size and BRAF mutation. Results: There were 7 cases of thyroid papillary carcinoma. The mean age of patients was (18.71 ± 2.75), and the mean tumor diameter was (2.4 ± 1.04) cm. Lymph node metastasis rate was 100% (7/7). In children and adolescents, the lesion volume was larger, membrane invasion and vascular cancer thrombus were more likely to occur, BRAF mutation was less common, and the difference was statistically significant. Conclusion: Children and adolescents with differentiated thyroid carcinoma are more aggressive and prone to membrane invasion and lymph node metastasis;BRAF mutation is less common than in adults.

Treatment Outcome of Papillary Carcinoma Confined to the Thyroid Isthmus

Objective: The purpose of this study is to evaluate the clinicopathologic characteristics and treatment outcomes of Papillary Thyroid Carcinomas (PTC) of the isthmus and to establish an appropriate surgical strategy. Methods: Thirty-four patients with PTC in isthmus are managed by surgery in National Cancer Center/Cancer Hospital of Chinese Academy of Medical Sciences, Peking Union Medical College from 1985-2008. Demographic data, surgical procedures, pathological features, stages and outcomes are analyzed. Results: Seven patients were men and 27 were women. The median age was 41 years (range, 20 - 71). Twenty-five patients were treated with thyroid isthmusectomy or wide field isthmusectomy, five with hemithyroidectomy (lobectomy and isthmusectomy) and four with hemithyroidectomy and partial resection of the contralateral lobe. Twenty-eight patients had a pathologically T1 lesion (pT1);two patients had a pT2 lesion and four had a pT3 lesion. Five patients (14.7%) had papillary carcinoma detected in one of the pretracheal lymph nodes. Thirty-two patients had a solitary lesion confined to the thyroid isthmus. One patient had two lesions in the thyroid isthmus and another one had two lesions located in the thyroid isthmus and right lobe respectively. With a median follow-up of 94 months (range, 12 - 274), two patients had a recurrence and both survived after a re-operation. There was no regional lymph node or distant organ recurrences. No deaths occurred. Conclusions: Isthmusectomy or wide field isthmusectomy could be a sufficient treatment for PTC confined to the thyroid isthmus. We also recommend that pretracheal lymph node dissection be considered.

Residual tumor and central lymph node metastasis after thermal ablation of papillary thyroid carcinoma: A case report and review of literature

BACKGROUND Debate exists regarding the use of thermal ablation(TA)to treat papillary thyroid carcinoma(PTC).Some studies have recommended TA as a new,ef
cient and safe technology for PTC.In this article,we report one case of a residual tumor and central lymph node metastasis(CLNM)after TA for PTC.CASE SUMMARY A 63-year-old female underwent bilateral ultrasound(US)-guided radiofrequency ablation for PTC.Three months later,she was diagnosed as thyroid cancer with suspected CLNM by US and contrast-enhanced computed tomography.The subsequent fine-needle aspiration(FNA)biopsies were negative.Due to her strong personal preference,she underwent total thyroidectomy and central lymph node dissection.Local tissue adhesion and a difficult dissection were noted during the operation.The pathology of the frozen sections during the operation was still negative.The final pathology results of paraffin-embedded sections revealed residual tumor cells at the edge of the PTC and CLNM.CONCLUSION TA may lead to a residual tumor in patients with PTC.Follow-up using US and FNA biopsy may not be adequate to evaluate the residual tumor.TA should be carefully considered in PTC treatment.

Relationship between subgroups of central and lateral lymph nodemetastasis in clinically node-negative papillary thyroid carcinoma

BACKGROUND Lymph node metastasis(LNM) of papillary thyroid carcinoma(PTC) has a certain regularity and occurs first to the central lymph node and then to the lateral lymph node. The pathway of PTC LNM can guide surgical prophylactic lymph node dissection(LND) for clinical surgeons.AIM To investigate the relationship between subgroups of central LNM and lateral LNM in unilateral clinically node-negative PTC(cN0-PTC).METHODS Data were collected for 1089 PTC patients who underwent surgical treatment at the Department of Endocrine and Breast Surgery of the First Hospital of Chongqing Medical University from January 2016 to December 2017. A total of 388 unilateral cN0-PTC patients met the inclusion criteria and were enrolled in this study. The clinical and pathological data for these 388 patients who underwent total thyroidectomy + central LND + lateral LND were retrospectively analyzed. The relationship between the central LNM and lateral LNM subgroups was investigated.RESULTS The coincidence rate of cN0-PTC was only 30.0%.Optimal scaling regression analysis showed that sex(57.1% vs 42.9%, P = 0.026), primary tumor size(68.8% vs 31.2%, P = 0.008), tumor location(59.7% vs 40.3%, P = 0.007), extrathyroid extension(ETE)(50.6% vs 49.9%, P = 0.046), and prelaryngeal LNM(57.1% vs 42.9%, P = 0.004) were significantly associated with ipsilateral level-II LNM. Their importance levels were 0.122, 0.213, 0.172, 0.110, and 0.227, respectively. Primary tumor size(74.6% vs 30.2%, P = 0.016), pretracheal LNM(67.5% vs 32.5%, P < 0.001), and paratracheal LNM(71.4% vs 28.6%, P < 0.001) were significantly associated with ipsilateral level-Ⅲ LNM. Their importance levels were 0.120, 0.408, and 0.351, respectively. Primary tumor size(72.1% vs 27.9%, P = 0.003), ETE(70.4% vs 29.6%, P = 0.016), pretracheal LNM(68.3% vs 31.7%, P=0.001), and paratracheal LNM(80.8% vs 19.2%, P < 0.001) were significantly associated with ipsilateral level-IV LNM. Their importance levels were 0.164, 0.146, 0.216, and 0.472, respectively.CONCLUSION The LNM pathway of thyroid cancer has a certain regularity. For unilateral cN0-PTC patients with a tumor diameter > 2 cm and pretracheal or ipsilateral paratracheal LNM, LND at ipsilateral level Ⅲ and level IV must be considered. When there is a tumor in the upper third of the thyroid with prelaryngeal LNM, LND at level II, level Ⅲ and level IV must be considered.