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1、Lung Cancer Staging Essentials: The New TNM Staging System and Potential Imaging Pitfalls（陷阱；易犯的错误） Stacy J. UyBico, MD Carol C. Wu, MD Robert D. Suh, MD Nanette H. Le, DO Kathleen Brown, MD Mayil S. Krishnam, MD, MRCP, FRCRAbstractLung cancer is the leading cause of cancer-related deaths worldwide,
2、 with a dismal（令人沮丧的；惨淡的，凄凉的） 5-year survival rate of 15%. TheTNM(tumor-node-metastasis) classification system for lung cancer is a vital guide for determining treatment and prognosis（预后）. Despite the importance of accuracy in lung cancer staging, however, correct staging remains a challenging task
3、for many radiologists. The new 7th edition of the TNM classification system features a number of revisions（修订）, including subdivision of tumor categories on the basis of size, differentiation between local intrathoracic and distant metastatic disease, recategorization of malignant pleural or pericar
4、dial disease from stage III to stage IV, reclassification of separate tumor nodules in the same lung and lobe as the primary tumor from T4 to T3, and reclassification of separate tumor nodules in the same lung but not the same lobe as the primary tumor from M1 to T4. Radiologists must understand the
5、 details set forth （提出；阐明）in the TNM classification system and be familiar with the changes in the 7th edition, which attempts to better correlate disease with prognostic （预后价值）value and treatment strategy. By recognizing the relevant radiologic appearances of lung cancer, understanding the appropri
6、ateness of staging disease with the TNM classification system, and being familiar with potential imaging pitfalls, radiologists can make a significant contribution to treatment and outcome in patients with lung cancer. IntroductionLung cancer is the leading cause of cancer-related deaths in the Unit
7、ed States, with a 5-year survival rate of only 15%(1). Lung cancer is classified as either nonsmall cell or small cell lung cancer, with the former accounting for 87% of all lung cancers (1). The descriptors of the internationally used TNM (tumor-node-metastasis) classification system for staging va
8、rious cancers include the size of and the degree of locoregional （局部）invasion by the primary tumor (T), the extent of regional lymph node involvement (N), and the presence or absence of intrathoracic or distant metastases (M). The goal of such a classification system is to assist clinicians in plann
9、ing treatment, determining prognosis, evaluating treatment results, and facilitating information exchange between multiple centers (2). The International Association for the Study of Lung Cancer (IASLC)（国际肺癌研究协会）serves as the primary source of recommendations for lung cancer staging revisions recogn
10、ized by the International Union Against Cancer (UICC)（国际抗癌联盟）(3). The much-anticipated 7th edition of the TNM staging system for lung cancer incorporates（合并） several proposed revisions to better align TNM staging with prognosis and, in some cases, with treatment (3-5), on the basis of evidence from
11、a significantly larger worldwide database that has been subjected to extensive validation（得到深入验证）(6). In this article, we discuss and illustrate each descriptor of the TNM staging system and present the changes within each subsection of the new 7th edition of the TNM system. In addition, we discuss
12、common pitfalls in lung cancer staging (nodal metastatic drainage patterns, incidental pulmonary nodules, mediastinal adenopathy, metastatic disease, chest wall and pleural invasion, and pleural-pericardial metastasis) and the relative merits of 2-fluorine-18fluoro-2-deoxy-D-glucose (FDG) （2-18F-2-脱
13、氧-D-葡萄糖）positron emission tomography (PET)（正电子发射型计算机断层扫描）, magnetic resonance (MR) imaging, and computed tomography (CT) in this setting. We also briefly discuss staging-based treatment regimens（方案）.Figure 1 shows the descriptors from the 7th edition of the TNM staging system for lung cancer (in a m
14、anner similar to Lababede et al7 ), whereas Table 1 compares and contrasts the 6th and 7th editions, with rationale (n.理论基础)given for the revisions in the newer edition (2-5,7-9). Figure 1. Chart illustrates the descriptors from the 7th edition of the TNM staging system for lung cancer.Table 1. Comp
15、arison of the 6th and 7th Editions of the TNM Staging System for Lung Cancer第七版肺癌TNM分期系统图释(T)原发肿瘤（T）T1aT1bT2aT2bT3T4大小2cm23m35cm57cm7cmAny支气管内占位未侵及近端叶支气管主支气管（距隆突2cm）主支气管（距隆突2cm）局部侵犯被肺组织或脏胸膜包绕脏胸膜胸壁/膈/纵隔胸膜/壁层心包膜纵隔/气管/心脏/大血管/食管/椎体/气管隆突其他肺不张/阻塞性肺炎累及肺门区但未累及全肺肺不张/阻塞性肺炎累及全肺；散发肿瘤结节与原发灶同侧肺、同叶散发肿瘤结节与原发灶同侧肺、非同
16、叶第七版肺癌TNM分期系统图释（N）锁骨上斜角肌纵隔隆突下肺门支气管周围（同侧）对侧同侧对侧同侧N3+N2N1N0第七版肺癌TNM分期系统图释（M）M1a（局限在胸腔内）恶性胸膜渗出/心包渗出；对侧肺散发肿瘤结节M1b（胸腔外转移）肝脏、骨骼、脑、肾上腺等第六、七版肺癌TNM分期系统对比分类第六版第七版修订原因T 大小肿瘤结节与原发灶同侧肺、同叶肿瘤结节与原发灶同侧肺、不同叶对侧肺T1：3cmT2：3cmT4M1M1T1a：2cmT1b：2cm but3cmT2a：3cm but5cmT2b：5cm but7cmT3：7cmT3T4M1a5年生存率=77%5年生存率=71%5年生存率=58%5
17、年生存率=49%5年生存率=35%5年生存率=28%（与T3近似，比T4稍好）5年生存率=22%（与T4相似）5年生存率=3%（与其他胸廓内转移相一致）N淋巴结图恶性胸膜渗出、心包渗出淋巴结分期依据MD-ATS（Mountain-Dresler-美国胸科协会）T4新出版的IASLC（国际肺癌研究协会）淋巴结图（图7）M1a新的IASLC淋巴结图协调了与早期淋巴结图的差异，并提供了淋巴结解剖学边界的描述，保证准确的淋巴结定位5年生存率=2%（与胸腔内转移相似，与其他T4期病人的15%形成对比）M 转移M0：无M1：有M0：无M1a：局限在胸腔内M1b：远隔或胸腔外转移其他结节如在对侧肺（M1a）
18、平均存活时间为10个月，一年生存率为45%平均存活时间为6个月，一年生存率为22%TNM DescriptorsTumorThe degree of primary tumor spread is represented by the T descriptor, which provides details regarding tumor size, local invasion, endobronchial location, and presence of separate tumor nodules. The T1 and T2 categories include subcategor
19、ization of size with new T1a, T1b, T2a, and T2b subdescriptors. Stage T1.Tumors less than or equal to 2 cm in maximum diameter are stage T1a tumors; those larger than 2 cm but smaller than or equal to 3 cm are stage T1b tumors (Fig 2).Figure 2. Stage T1 tumors. (a) Chest CT scan shows a left lower l
20、obe nodule (arrow) measuring less than 2 cm in size, a finding that is consistent with a stage T1a tumor (2 cm). (b) Chest CT scan obtained in a different patient shows a right upper lobe nodule (arrow) measuring 2.9 cm in size, a finding that is consistent with a stage T1b tumor (2 cm but 3 cm). Tu
21、mors surrounded by lung or visceral pleura and endobronchial lesions without invasion proximal to（近端，以上） a lobar bronchus are still considered stage T1 tumors as in the earlier edition. Stage T2.Tumors larger than 3 cm but smaller than or equal to 5 cm are stage T2a tumors (Fig3a); those larger than
22、 5 cm but smaller than or equal to 7 cm are stage T2b tumors. Figure 3. Stage T2 tumors. (a) Chest CT scan shows a centrally located lung nodule (arrow) causing airway obstruction, with atelectasis or postobstructive pneumonia that does not, however, involve the entire lung. (b) Chest CT scan obtain
23、ed in a different patient shows a mass in the right lung (arrow) measuring 4.8 cm, a finding that is consistent with a stage T2a tumor (3 cm but 5 cm). (c) Coronal chest CT scan obtained in a third patient shows a nodule in the bronchus intermedius （气管中间）(arrow). The nodule is 4 cm from the carina (
24、an endobronchial lesion 2 cm from the carina is considered stage T2). At histopathologic analysis, the nodule proved to be a squamous cell carcinoma. Tumors with local invasion of the visceral pleura alone, with possible atelectasis（tilektsis肺不张） and obstructive pneumonitis （nju:munaitis肺炎）extending
25、 to the hilar region but not involving the entire lung, are considered stage T2 tumors. Endobronchial lesions more than 2 cm distal to the carina （隆突）also belong in this category (Fig 3b,3c).Stage T3.Tumors larger than 7cm are now considered stage T3 tumors (Fig 4c). Separate tumor nodules in the sa
26、me lobe as the primary lesion are now in the T3 category as well (Fig 5). Figure 4. Stage T3 tumors. (a) Chest CT scan shows an irregular mass in the left upper lobe with suspicious local extension to the mediastinal pleura (arrow), a finding that was subsequently confirmed at surgery and histopatho
27、logic analysis. (b) Chest CT scan obtained in a different patient shows an endobronchial mass (arrow) less than 2 cm from the carina. Pathologic analysis confirmed malignant carcinoid tumor, which can be staged using the 7th edition of the TNM staging system. (c) Chest CT scan obtained in a third pa
28、tient shows a left lower lobe mass over 7 cm in diameter (arrow). Figure 5 . Stage T3 tumors. Chest CT scan shows a primary mass (arrow) with satellite nodules (arrowheads) in the right lower lobe. This is considered stage T3 disease in the 7th edition (stage T4 disease in the 6th edition). Endobron
29、chial lesions less than 2 cm distal to the carina (Fig 4b); tumors with local invasion of the chest wall, diaphragm, mediastinal pleura, and parietal pericardium; superior sulcus tumors（上沟癌）; and tumors with atelectasis and obstructive pneumonitis affecting the entire lung are still considered stage
30、 T3 neoplasms. Stage T4.Stage T4 tumors include separate tumor nodules in the same lung but not in the same lobe as the primary lesion, which were previously considered metastatic (M1) (Fig 6). In addition, the presence of a malignant pleural effusion, pleural dissemination, or pericardial disease n
31、ow constitutes metastatic disease (M1a) and is no longer in the T category (3). Figure 6 . Stage T4 tumors. Chest CT scan shows a primary lung tumor in the right upper lobe (long arrow) with a smaller separate nodule in the right lower lobe (short arrow). In the 7th edition, this is considered stage
32、 T4 disease (stage M1 metastatic disease in the 6th edition). However, tumors of any size that demonstrate local invasion of the mediastinum or carina, trachea, heart, great vessels, esophagus, or vertebral bodies are still considered stage T4 tumors (Fig 7). Figure 7. Stage T4 tumors. Chest CT scan
33、 shows a right upper lobe mass (arrow) with mediastinal and carinal invasion, ipsilateral loculated（分为小腔的） pleural effusion, and thickening and enhancement of the pleura. Note the tumor encasement and resultant narrowing of the right main-stem bronchus (arrowhead). The pleural thickening and enhance
34、ment, although nonspecific, are suggestive of metastatic pleural disease. In the 7th edition, proved pleural carcinomatosis（癌变，癌扩散） is considered stage M1a disease (stage T4 in the 6th edition). The 7th edition of the TNM staging system includes several changes to the T category (4). 1. There are se
35、veral new size criteria subcategories. The new tumor size limits of 2, 3, 5, and 7 cm (to differentiate between stages T1a, T1b, T2a, T2b, and T3) are markedly different from those in the 6th edition, in which only a single size limit of 3 cm is used for differentiation between T1 and T2 tumors.2. B
36、ecause of statistically significant findings of survival rates, stage T4 disease is downgraded to stage T3 when satellite nodules（卫星病灶） are present in the same lobe as the primary lesion, and stage M1 disease is downgraded to stage T4 when nodules are present in the same lung but not the same lobe a
37、s the primary lesion.3. The presence of malignant pleural effusion, pleural dissemination, or pericardial disease is now considered metastatic diseasespecifically, stage M1a for local intrathoracic diseaserather than stage T4 disease.NodeLymph nodes measuring 1 cm or more in the short axis are consi
38、dered significant in size and suspicious for metastatic disease, although the predictive accuracy of this criterion is limited (10,11). Although the IASLC（国际肺癌协会） proposed a new lymph node map that reconciles the differences between the previous nodal maps and provides detailed anatomic and zonal de
39、finitions for all lymph node stations (Fig 8,Table 2), there are no changes to the N descriptors in the 7th edition of the TNM staging system. This retention （保留，保持）of the earlier descriptors is due to the difficulty of obtaining large patient samples with precise lymph node staging that could be an
40、alyzed across each T stage to obtain statistically valid results (8). Figure 8. Drawings and chart illustrate the new IASLC lymph node map, which reconciles differences between earlier nodal maps including the Naruke and MD-ATS (Mountain-DreslerAmerican Thoracic Society) maps. The new nodal station
41、numbers and names are shown, including the grouping of stations into “zones” for future prognostic analyses. Ao = aorta, AP = anteroposterior, Eso = esophagus, mPA = main pulmonary artery, SVC = superior vena cava, T = trachea. (Reprinted, with permission, from reference.) Table 2. IASLC Anatomic De
42、finitions for Lymph Node StationsStage N1.Lymph nodes in the hilar, interlobar, lobar, segmental, and subsegmental regions are considered stage N1 disease (Fig 9). Figure 9. Stage N1 lymph nodes. (a) Chest CT scan obtained in a patient with right-sided lung cancer shows an enlarged right hilar lymph
43、 node (level 10) (arrow) measuring 15 mm in the short axis. (b) Chest CT scan obtained in a different patient shows a left lower lobe mass and an ipsilateral enlarged interlobar lymph node (level 11) (arrow) measuring 11 mm in the short axis. Stage N2.Lymph nodes in the ipsilateral mediastinum are c
44、onsidered stage N2 disease. Affected anatomic regions include the upper paratracheal, prevascular and retrotracheal, lower paratracheal, subcarinal, paraesophageal, and pulmonary ligament regions (Fig 10). Figure 10. Stage N2 lymph nodes. (a) Chest CT scan shows an enlarged (1.6-cm) right upper para
45、tracheal lymph node (level 2) (arrowhead). (b) Chest CT scan obtained in a different patient shows an enlarged (1.5-cm) right lower paratracheal lymph node (level 4) (arrowhead). Like the lymph node in a, it is clearly to the right of the new border proposed by the IASLC (ie, the left lateral border
46、 of the trachea). (c) Chest CT scan obtained in a third patient shows a right lower lobe mass (white arrow) with an enlarged (1.6-cm) subcarinal lymph node (level 7) (black arrow). Stage N3.Lymph nodes on the side opposite the primary tumor, and all significantly large lymph nodes in the ipsilateral
47、 or contralateral supraclavicular or scalene regions, are considered stage N3 disease (Fig 11). Figure 11. Stage N3 lymph nodes. (a) Axial PET/CT image of the chest shows a primary mass in the left lung (arrow) and a right lower paratracheal lymph node (arrowhead), both of which demonstrate intense radiotracer uptake. Metastatic involvement of the lymph node was confirmed at mediastinoscopic resection. (b) Chest CT scan obtained at the lung apex in a different patient shows enlarged bilateral supraclavicular lymph node
