OBJECTIVES: Lymphatic involvement is believed to be relatively rare in thymic epithelial tumours. The incidence and prognostic significance of nodal metastases are still unclear. The goal of this study was to define the incidence and prognostic relevance of nodal metastasis in patients with thymic epithelial tumours, using a nationwide retrospective database of the Chinese Alliance for Research in Thymomas. METHODS: Patients who underwent upfront surgical resection without preoperative therapy were enrolled for the study. The International Thymic Malignancies Interest Group proposal of a new staging system for thymic epithelial tumours was used to redefine the pathological stage. The incidence of nodal metastasis and its relationship with clinicopathological characteristics and its impact on survival were examined accordingly. RESULTS: A total of 1617 patients were enrolled in this study. Lymph node metastasis was identified in 35 patients (2.2%). No nodal involvement was found in type A, AB or B1 thymomas. The incidence of nodal metastasis in thymoma (B2/B3) and thymic carcinoma was 1.3% and 7.9%, respectively, and it was most commonly seen in patients with neuroendocrine thymic tumours (16.7%, P< 0.001). According to the primary tumour invasion stage, incidences of nodal metastasis were 0.2% in T1, 6.9% in T2, 8.5% in T3 and 7.4% in T4 tumours (P< 0.001). Gender, pleural or distant metastasis and resection status were also correlated with nodal metastasis (P < 0.05) in univariable analysis. Multivariable analysis revealed that patients with non-thymoma histological characteristics (P < 0.001) and tumours in non-T1 stage (P < 0.001) had significantly greater risk of developing nodal metastasis. The overall survival of patients without nodal metastasis was significantly higher than that of patients with nodal involvement (P < 0.001). Disease-free survival of patients after R0 resection without nodal metastasis was also significantly higher than those with nodal metastasis (P < 0.001). On multivariable analysis, overall survival was significantly associated with histology of the tumour (P=0.019) and complete resection (P = 0.047), and there was a trend towards significance (P= 0.052) in the association between overall survival and nodal involvement. CONCLUSIONS: Lymph node metastasis in low-grade, early stage thymic tumours is a rare phenomenon. However, it is not uncommon in tumours with a higher stage or a higher histological grade, especially in neuroendocrine thymic tumours. Nodal involvement as well as tumour invasion and histological grade may denote worse prognosis. Lymph node dissection may be warranted in selected high-risk patients.
[1]Shanghai Jiao Tong Univ, Shanghai Chest Hosp, Dept Thorac Surg, 241 Huaihai Rd West, Shanghai 200030, Peoples R China.
[2]Qingdao Univ, Dept Thorac Surg, Affiliated Hosp, Qingdao, Peoples R China.
[3]Sun Yat Sen Univ, Dept Thorac Surg, Guangdong Esophageal Canc Inst, Collaborat Innovat Ctr Canc Med,Canc Ctr,State Ke, Guangzhou, Guangdong, Peoples R China.
[4]Fudan Univ, Zhongshan Hosp, Dept Thorac Surg, Shanghai, Peoples R China.
[5]Tianjin Med Univ, Dept Endocrinol, Gen Hosp, Tianjin, Peoples R China.
[6]Sichuan Canc Hosp, Dept Thorac Surg, Chengdu, Sichuan, Peoples R China.
[7]Fujian Med Univ, Dept Thorac Surg, Union Hosp, Fuzhou, Fujian, Peoples R China.
[8]Anhui Med Univ, Dept Thorac Surg, Affiliated Hosp 1, Hefei, Anhui, Peoples R China.
[9]Zhengzhou Univ, Affiliated Canc Hosp, Dept Thorac Surg, Zhengzhou, Henan, Peoples R China.
[10]Beijing Canc Hosp, Dept Thorac Surg, Beijing, Peoples R China.
[11]Changhai Hosp, Dept Cardiothorac Surg, Shanghai, Peoples R China.
[12]Liaoning Canc Hosp, Dept Thorac Surg, Shenyang, Peoples R China.
[13]Jilin Univ, Dept Thorac Surg, Affiliated Hosp 1, Changchun, Jilin, Peoples R China.
[14]Sichuan Univ, West China Hosp, Dept Thorac Surg, Chengdu, Sichuan, Peoples R China.
[15]Fudan Univ, Huashan Hosp, Dept Thorac Surg, Shanghai, Peoples R China.
[16]Tianjin Canc Hosp, Dept Esophageal Canc, Tianjin, Peoples R China.
[17]Zhejiang Canc Hosp, Dept Thorac Surg, Hangzhou, Zhejiang, Peoples R China.
[18]Jiangxi Peoples Hosp, Dept Thorac Surg, Nanchang, Jiangxi, Peoples R China.
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