Smokers' Lungs

I am >> in Canada as elsewhere. Diseases of the lungs are a major health concern. In recent years, three types of projects in particular have helped to give us a much clearer understanding of what actually happens to the lung tissues as a result of cigarette smoking. >> One of these is the study of lungs at autopsy in both smokers and non-smokers. A second is the study of tissues removed at the time of surgical operation. And the third is examination under the microscope of that type of material that is coughed up from the lungs in both again smokers and non-smokers. Much of this work is carried out in our department in attempts at earlier diagnosis of lung cancer. Specimens are first processed and then analyzed by our staff in the laboratories. Any abnormalities which may be found are marked for further study. As a result of these combined studies, we now have a series of slides which presents a comprehensive picture of what actually happens over a long period of time in these lungs. The changes that I am emphasizing here primarily by the way are those related to the development of lung cancer. The changes of chronic bronchitis and emphyma are also very important in the context of the effects of smoking on the lungs but these are the subject of separate studies and merit separate discussion. This first slide is a view under the microscope of the bronchial tube or air passage surrounded by the lining membrane of the airway. This lining membrane normally has two functions. You'll notice along the surface there are these fine hairlike structures called psyia and these are constantly moving in a wavelike fashion as a result of which any impurities deposited on the surface of the lung are propelled upwards and removed from the lung. This process of cleansing the lung is aided by the second function which is the secretion of mucinous material or flem from some of these cells in the area. This sticky fle oozes out onto the surface and inhaled impurities are deposited on this material. These two important functions in the normal lung keep the airway clear and free from impurities. The air that we breathe is not completely pure. There are always small amounts of pollution which we inhale. However, there is a major difference between the level of impurity in the atmosphere in which we live and the very high level of impurity in inhaled cigarette smoke. In this next slide are some of the individual cells that is the individual units which make up the lining membrane of the airway. We can see these under the microscope. If a sample of sputum material is smeared on a slide and then stained, these cells are normally replaced by others of the same kind after they have become worn out or have exhausted their function and are then cast off into the sputum for removal. At the end of each of these individual cells are these small hairike structures which have been moving the impurities back up the bronchial tree against the force of gravity. Remember the appearance of these cells in this normal state. Later you will see how different these cells are from those which are cast off after the membrane from which they originate has become cancerous. The first of a series of changes that we see with cigarette smoking is evident in this slide. Instead of clean secretion from the lung containing a few of the normal cells that are being released and replaced by similar new cells, we see accumulations now of these so-called scavenger cells. One might say that this is a secondary line of defense in an attempt to cope with this extremely high concentration of impure material in the inhaled cigarette smoke. These cells, as you can see, have taken up or have ingested numerous particles of carbon and tar material which have been inhaled in the smoke. Large numbers of these scavenger cells emerge from the lung tissues, take up this material and are then carried away in the flem which is coughed up. The sputum of a cigarette smoker characteristically shows massive accumulations of these cells. The next two slides will show that even this line of defense is overwhelmed and is quite ineffective eventually because the lungs in a cigarette smoker gradually become blackened in appearance. First is an example of a normal adult lung showing a fresh pinkish color even though this was a lung from a city dweller. In contrast, this lung from a cigarette smoker shows extensive black discoloration and a rather coldlike appearance on this cut surface. This discoloration in the lung of a heavy cigarette smoker begins to develop in the late high school years and even in the early 20s. One can see significant amounts of this black deposit. Nature had never intended that the lung should cope with this degree of inhalation of impurities and so the cleansing mechanism simply cannot cope with its removal. Much of this material becomes permanently deposited in the lung tissues. If we now take another look at the lining of the airway under the microscope, we see abnormality in the lining membrane which has been developing simultaneously as a result of irritation from the smoking. In reacting this way, the membrane has become thicker and more resistant. But in doing so, it has sacrificed the normal functions of secretion and cleansing activity and no longer produces the flamm which helps to remove the impurities. The little hairike structures are damaged and finally disappear completely from the surface. This has now become a more hardy type of membrane which is more resistant to the irritation from smoke. But this area of the lung can no longer function in a normal way. After a longer period of time, this change becomes complete and the affected area has been converted to this thick, dry and leathery type of lining. This process is a rather prominent phenomenon in the early years of smoking. Over the ensuing years with further smoking, the changes progress gradually farther and farther out along the air passages. Inhaled material tends to accumulate beyond these areas and become stagnant resulting in irritation and the smoker's cough. The lung has now become more susceptible to infections generally. Continuing damage to the lining results in more serious changes. This slide shows the abnormal leathery type of lining at these margins where the regular pattern of structure indicates that even though it is abnormal, it is still benign. In the central area, however, something has gone wrong with the cells. They are irregular in appearance, have become disorganized. They no longer recognize normal limiting boundaries and have begun to encroach on the adjacent normal tissues. These are the first signs of actual cancerous change. These bizarre changes have been induced in the cells after the stress of prolonged and repeated attempts to repair the membrane which has been damaged by this continued irritation. The metabolism within these cells is now abnormal and the activity of these cells no longer follows a normal pattern. This abnormality gradually involves more of the membrane over a period of years. There are however no new or unusual symptoms associated with its insidious progression. In this next slide on the right are the bizarre individual cells which may be shed from this type of abnormal tissue. Here on the left in contrast you will recognize the benign normal cells of the type which were originally shed from this area. These cancerous cells bear little resemblance to their normal counterpart. Now the next few slides will show a series of stages in the cancerous chain. Though too small to cause symptoms, the abnormality slowly becomes a visible thickening in the lining of the bronchial tube. This small area with a rough appearance over the surface is the first sign of cancer which is visible without a microscope. However, if we examine a small portion of this tumor after preparation for study under the microscope, we can see that the cancerous tissue is already invading into the deeper areas. This slide, by the way, shows how cancer got its name. Many years ago, when cancer and other tissues were first observed under the microscope, the observers were impressed by these clawike processes or extensions of cancer as it invaded into the adjacent normal tissues. These seem to resemble the claws of a crab, and the Latin name for crab is cancer. In the center of this slide, you'll notice a small blood vessel. When the tumor eventually invades into the blood vessel, small fragments will break off into the bloodstream. and then spread to other parts of the body. In this next slide, this small tumor has reached the stage where it is almost blocked off one of the air passages. In this cross-section of a slightly more advanced cancer almost blocking the airway, it is interesting to note the black deposits that have accumulated in the lung over the years. You can see that the cancer is not developed in these areas where the deposits are located. Instead, it has developed, as most lung cancers do, in the exposed lining of the air passages. We find, therefore, that the chronic continued irritation of the smoking seems to be important in addition to whatever chemical factor may be present. This tumor, by the way, would not yet be visible in a chest X-ray. It has not formed a mass outside the wall of the bronchial passage. This slide shows a lung which has been sliced open to reveal a cancer which has progressed to this relatively advanced stage before the patient became aware of any related symptoms. The lung does not contain sensitive nerve endings. So cancer of the lung in the early stages is not painful which in a way is unfortunate. This X-ray film of the chest illustrates again the relatively advanced stage of the tumor at the usual time of its discovery because of symptoms. The cancer has already become quite large and very probably would have spread by this time to other areas. of every hundred patients with lung cancer discovered at this stage approximately 10 only would survive even two years. So as you can see the effects of smoking on the lung are both diverse and insidious and the fact that these changes are progressing slowly at this moment in millions of lungs is discouraging for those of us who value healthy human life.