Hi, my name is Leslie Quint. I'm from the Department of Radiology at the University of Michigan. And today, we'll be talking about primary tumor or T staging for lung cancer. The objectives for this talk are to review the definitions of the primary tumor stages in the current TNM staging classification system for lung cancer. This is the eighth edition of the classification system. Along the way, we'll review imaging features that help to indicate the T stage. Let's start out with a pre-lecture question. This is a CT scan from a patient who presented with hemoptysis, cough, and chest pain. The CT shows a tumor mass which is here, which is obstructing the right upper lobe bronchus and it is extending into the distal right mainstem bronchus. Notice, that there is post-obstructive consolidation of the entire right upper lobe. Here is your question, what is the presumed T stage? Would you choose T1, T2a, T2b, or T3 disease? Go ahead and pick your best option and we'll get back to this at the end of the talk. Okay, so let's get started. The International Association for the Study of Lung Cancer made changes to the TNM classification system in order to better align this system with patient prognosis. This led to the eighth edition of the lung cancer staging classification system. This was released in January of 2017. However, it was decided that in the United States, we would hold off on implementing the system until January of 2018. So let me just basically summarize the T stage changes before we look at some illustrations. First of all, there's a greater emphasis on primary tumor size recognizing a strong correlation between tumor size and tumor prognosis. To that end, lower T subcategories are now designated using one centimeter size increments and larger tumors have been shifted into higher T subcategories. There are various other shifts leading to up and down staging and we'll go over those during this talk. Let's start with the T1 lesions. These are the small cancers, no more than three centimeters in greatest dimension, surrounded by lung, as we see on this example over here, or surrounded by visceral pleura. These cancers do not involve a main bronchus. T1 is broken down into size increments as follows: The T1a cancers are no more than one centimeter in diameter, as shown in this example. The T1b lesions are from 1-2 centimeters in diameter and the T1c lesions are from 2-3 centimeters in diameter. There's a new category called T1a(mi). These are the minimally invasive, early bronchogenic adenocarcinomas. They are solitary and they show a predominantly lepidic pattern under the microscope and there's no more than five millimeters of stromal invasion in greatest dimension. This is a histologic category, but we do see a correlate on our CT scans. Generally, these lesions show up as small subsolid nodules, like this one, that are mostly ground glass but they have a small central solid component. It is the solid component that corresponds to the area of invasions, so the solid component should be no more than five millimeters in diameter. Let's move on to the T2 cancers. These are larger, from 3-5 centimeters in greatest dimension, as we see in this example. T2 cancers may involve a main bronchus regardless of the distance to the carina as long as the carina itself is not involved, and the reason that I have this in a different font color is because this is a change from the previous classification system. In this example, the patient has a right upper lobe bronchogenic carcinoma, it is narrowing the right upper lobe bronchus and more importantly, it is invading directly into the right main bronchus and therefore this is a T2 cancer. The T2 category also includes invasion of the visceral pleura and that is suggested in this patient with a left upper lobe cancer that shows broad contact with the pleural surface. Also in the T2 category, we see cancers with post-obstructive atelectasis or pneumonia that extends to the hilum and this may involve part of the lung or the entire lung and that is different than the previous classification system. In this patient, the CT scan shows a central right upper lobe mass, occluding the right upper lobe bronchus with post-obstructive atelectasis and similar findings are seen here on the fused CT pet image. So post-obstructive atelectasis makes this a T2 lesion. Just like the T1 category, T2 is also broken down by size. The T2a lesions are from 3-4 centimeters in diameter, and the T2b lesions from 4-5 centimeters in diameter. Moving onto the T3 category, these are larger cancers from 5-7 centimeters in greatest dimension. The T3 category includes chest wall invasion and here are two examples on our imaging studies. On CT scanning, we look for frank rib destruction, as we see here, and in a different patient, on MR scanning, we'd look for disruption of the extrapleural fat plane as we see here. So these findings are indicative of chest wall invasion and that puts these tumors into the T3 category. T3 also includes superior sulcus invasion as illustrated in this patient on an MR scan. We see a tumor here at the apex of the lung, it's growing out of the lung into the adjacent soft tissues here on a sagittal MR image and here on a coronal MR image. And in fact, MR is the modality of choice in diagnosing superior sulcus invasion and that would again constitute T3 disease. MR is also the modality of choice in looking for associated brachial plexus involvement by these types of tumors. T3 category also includes tumors that invade the phrenic nerve and/or the parietal pericardium. In this example, there's a large central left upper lobe mass and we see the parietal pericardium over here. Notice, that the tumor is abutting the pericardium so that may be invaded. More to the point however, we see elevation of the left hemidiaphragm and that is consistent with involvement of the phrenic nerve, which would live in this region. In the T3 category we also have separate tumor nodules in the same lobe of the lung. So in this patient we see severe underlying smoking-related emphysema and there are two nodules, both of these were cancers so this constitutes T3 disease, both on the same lobe of the lung. Finally, the T4 category, these are the very large cancers more than seven centimeters in greatest dimension. The T4 category includes invasion of all of the structures listed here. So let's go through these and look at some examples and we'll start with diaphragmatic invasion. This used to be in the T3 category but that has now been upstaged to T4 because these patients are filled to have a poor prognosis. In this example, the patient has a right lower lobe cancer which is here, it's indenting the liver but it's surgery had not actually invaded the liver. The tumor had invaded the diaphragm and the surgeons needed to resect this portion of the diaphragm and reconstruct it. So this is T4 disease diaphragmatic invasion. Also on the T4 category is mediastinal invasion. Sometimes the invasion is gross as we see in this example, where there's extensive soft tissue throughout the mediastinal fat. In other patients there's only minimal mediastinal fat invasion but that also counts as T4 disease. Moving on, in the T4 category, we sometimes see invasion of the heart and the great vessels. In the example on top, notice the tumor is invading directly into the main pulmonary trunk and in the patient on the bottom, there is tumor invasion of mediastinal fat so that by itself is T4 disease and in addition the tumor is invading into the superior vena cava, that is also T4 disease. In the patient illustrated here, the pet scan shows a large central right lung mass extending into the subcarinal region. So that is T4 cancer. In addition on the coronal CT image, we see the tumor extends right up to the subcarinal area just below the carina. At bronchoscopy there was tumor invasion into the central airway. So invasion of the trachea or the carina as in this patient is a T4 cancer. Involvement of the recurrent laryngeal nerve also falls into the T4 category and here's a rather typical example, the tumor masses in the aortopulmonary window, and that's where the left recurrent laryngeal nerve loops underneath the aortic arch, and if we look up in the lower neck, we can see asymmetry of the vocal cords. So the left recurrent laryngeal nerve was invaded and it was causing left vocal cord paralysis, that's T4 disease. In the example shown here, there's a central right upper lobe mass. Notice that it is encasing the right subclavian artery and the right common carotid artery. If those arteries are actually invaded, that would be T4 disease. In addition, the tumor abuts the esophagus and endoscopy there was tumor invasion through the wall of the esophagus. So esophageal invasion is T4 cancer. Finally, invasion of the vertebral body also falls into the T4 category. In this patient, we see a left upper lobe mass growing into and destroying the vertebral column here. So vertebral invasion is T4 disease. Also included in the T4 category, we see separate tumor nodules in different ipsilateral lobes. If the two tumor nodules are in the same lobe of the lung, that would be T3 disease. If they're in different ipsilateral lobes, that constitutes T4 disease. So in this patient there's a speculated left upper lobe cancer. There's another cancer here in the left lower lobe. On the pet scan, we can see both the upper lobe lesion and the lower lobe lesions are FDG avid. These are both cancers and this is T4 disease and that brings us to our post-lecture question. So, just as a reminder this is a patient who presented with hemoptysis, cough, and chest pain. We notice that there is a small tumor nodule here, obstructing the right upper lobe bronchus and extending into the distal right main bronchus with post-obstructive consolidation of the entire right upper lobe. So, what do you think the presumed T stage is? Go ahead and pick your best choice. The best choice here would be T2a disease. This is a T2 cancer for two reasons. First of all, there's involvement of the main bronchus and secondly, there's post-obstructive atelectasis or pneumonia extending to the hilum. The reason this is T2a and not T2b is because of the size of the lesion, the lesion is no more than four centimeters in diameter. And that brings us to our take home points. First of all, in the new staging classification system, there have been significant changes to the T descriptor and the changes have been made in order to better predict patient prognosis. There are various imaging findings that are characteristic of the different T stages and can be helpful in determining the proper T stage. Thank you for your attention.
