Oral 3.04: The extent of lymph node dissection in thymic malignancies
In Kyu Park, Yoohwa Hwang, Samina Park, Eung Rae Kim, Chang Hyun Kang, Young Tae Kim
Background: The proper extent of lymph node dissection (LND) is unclear in thymic malignancies. We investigated the pattern of lymph node metastasis in thymic malignancies based on new ITMIG proposal for lymph node map for thymic malignancies.
Methods: We retrospectively reviewed 131 thymic malignancy patients who underwent total thymectomy and LND. New ITMIG/IASLC proposals for nodal map and TNM stage classification for thymic malignancies were used for lymph node grouping and TNM staging. Pattern of node metastasis and clinic-pathologic factors affecting node metastasis were analyzed.
Results: A total of 1,348 lymph nodes were dissected in 131 patients. The mean number of dissected lymph node was 10.3±8.5 (range: 1–48). A total of 582 anterior regional (N1) lymph nodes were dissected in 107 (81.7%) patients and 517 (88.8%) nodes were peri-thymic, prevascular nodes and lower anterior cervical nodes. A total of 766 deep regional (N2) nodes were dissected in 83 (63.4%) patients. The right paratracheal lymph nodes were dissected in consist 63.4% (486/766) of N2 nodes. Node metastasis was detected in 13 (N1–6, N2–7) patients. Six patients had metastasis at peri-thymic lymph nodes and two patients had metastasis at the prevascular lymph nodes. Six (86%) N2 patients had right paratracheal nodes (RPN) metastases. Node metastasis rates were 1% in T1 and 37.5% in T2/3 (P<0.001). Node metastasis rates were 8% in M0 and 43% in M1 (P=0.03). Node metastasis rate was higher in thymic carcinoma (25%) than thymoma (5.1%) (P=0.01). Node metastasis rates between subtypes of thymoma were also different. There was no node metastasis in A, AB and B1 types. Tumor size was also significant factor for node metastasis. The optimal cut-off value for the node metastasis was 6 cm and the specificity was 62%. Only 16% of patients got preoperative histologic diagnosis. The specificity for the prediction of node metastasis was 100% when T and M stages are combined (stage ≥ II). Freedom from recurrence rate of pN1/2 was significantly worse than pN0 (5-year: 38.5% vs. 87.9%, P<0.001).
Conclusions: Routine en bloc dissection of peri-thymic lymph nodes is recommended during thymic malignancy surgery and the right paratracheal lymph node should be dissected in thymic malignancies ≥ stage II.
Keywords: Lymph node dissection (LND); lymph node metastasis; thymic malignancy
doi: 10.3978/j.issn.2072-1439.2015.AB065
