 This is Dr. Shomali Kosh and I am going to talk on Solitary Pulmonary No-Jewel. We start off with the definition. It is a poorly defined or well-defined approximately rounded structure surrounded by lung patterned chimera measuring less than 3 cm in size in the absence of adenopathy and pleural disease. Now 90% of these SPNs are incidental findings. Why is it important? Because it is a possible alert signal for lung cancer. Extra pickup rate is 0.09% to 2%. CT scan pickup rate is obviously higher. It is 8 to 51%. And the frequency of the pickup rate will depend on, number one, endemicity of granulomatous disease, which means that it is more frequent in areas where tuberculosis is common. And whether we are looking at an at-risk population. This at-risk population means it is a population where smoking is more common, elderly is more common and whether people have got previous history of cancer, whether people have got asbestos exposure. And we are going to discuss about at-risk population in more details later on. Let us look at the nodule measurement and technical parameters of imaging. Images must be in full inspiration. Nodules are viewed and measured in thin slices less than 1.5 mm using high spatial frequency algorithm in order to avoid partial volume averaging and to detect any fat or calcification. Measurements are usually done in the axial plane and the accuracy of measurement is more in lung window. Now anything less than 3 mm are called micro nodules. These need not be measured at all. 3 to 10 mm nodules are measured for risk estimation. It is the average of short and long axis diameter rounded to the nearest whole millimeter, which means in this case the long axis is 0.77, the short axis is 0.61. You add the two, divide by two and it comes to 6.9. Now you rounded off to the nearest whole millimeter and this nodule measures 7 mm. Any nodule which is more than 10 mm should be measured in both the axes. So both the measurements need to be given. So once you see a SPN, what is the first thing that you need to do? It is important to secure the old film to see whether a nodule is new, old, stable or growing over time. Then we look for definitely benign features. If there are benign features, there is nothing to worry. If there is it, then we have to assess for the risk of malignancy. And we follow it up accordingly. So what are these definitely benign features? One is calcification. Two is nodule with macroscopic fat. Three is peripheral nodules. Four is nodules with long term stability. Five is small nodules in young patients. So there is a pattern of calcification which we can call definitely benign. It should be either diffuse like this, central, laminated or popcorn like. These kinds of calcifications are definitely benign. So that is diffuse calcification, laminated calcification, central calcification and of course the popcorn calcification of haematoma. So what is the second feature to call it benign? A nodule with macroscopic fat. We are looking at a haematoma. Third is the peripheral nodules. Peripheral nodules are definitely benign. What are they? They are homogeneous, smooth, solid, lentiform and triangular shaped nodule either within 1 centimeter of fissure or pleural surface and measuring less than 10 millimeters. So these are the typical peripheral nodules. Why? This is lentiform or triangular. This is atypical, may not be so lentiform or triangular but they are still very small, less than 1 centimeter. And these are the non-PFNs. They are unlikely to be peripheral nodules. Why? Because they are roundish in structure or speculated and they are larger in size. So here is a typical PFN and here is a non-PFN. Nodules with long-term stability. Solid nodules if they are stable for 2 years we call them benign. Sub-solid nodules if they are stable for 3 years and nowadays they say for 5 years then we can call it benign. Small nodules in young patients. How small? Less than 8 millimeters. And how young? Less than 35 years. So if we see a nodule which is less than 8 millimeters in a patient less than 35 years we can call it benign. So once we have called a nodule benign we have got nothing to worry. If not then we have to assess for the risk of malignancy. Let us look at the history for risk factors. Firstly, age. The probability of malignancy increases with age. 35 to 39 years is 3 percent. 40 to 49 years 15 percent. 50 to 59 years 43 percent. And more than 60 years 50 percent. Secondly, female sex. More prone to have malignant nodules. Smokers 10 times more in smokers. Past history of any malignancy asbestos exposure. Patients having emphysema or idiopathic pulmonary fibrosis. So all these patients were at risk of having malignancy. Now let us look at the radiological predictors of malignancy. Size, the larger the size the more the chances of it to be malignant. A nodule with spiculated margin or lobulated margin, upper lobe location if the calcification is asymmetric, cavitation and sub-solid appearance. Let us see why size is important. Anything less than 4 millimeter 0 percent chance, 4 to 7 millimeters 1 percent, 8 to 20 millimeters 15 percent and anything more than 20 millimeter 80 percent chance of malignancy. A nodule with spiculated margins definitely malignant. Upper lobe location, more chances of malignancy. Cavitation, anything less than 7 millimeters wall thickness likely to be benign. Anything more than 24 millimeters likely to be malignant. This was all in a recent study but there is actually no definite measurement which we can call it benign or malignant. We have discussed about benign calcification now look at the malignant calcification eccentric calcification like this in adenocarcinoma or carcinoid speckle calcification in adenocarcinomas. So these are malignant calcifications. Sub-solid nodules. Nodule having some ground glass opacities we are going to discuss about this in more details later. Far more chances for these kind of nodules to be malignant than the solid nodules. So now we know what the at-risk group was. And we follow up the solid nodules accordingly. We follow the Fleschner Society guidelines. So the low-risk group if it is less than 6 millimeter no follow up is required. For 6 to 8 millimeters CT at 6 to 12 months needs to be done. For the high-risk group less than 6 millimeter you can do a CT after 12 months. For 6 to 8 millimeters CT at 6 to 12 months and then follow it up at 1.5 to 2 years. Any nodule which is more than 8 millimeter cancer risk is 9.7 percent. If it is low-risk surveillance at 3 months is required. If it is high-risk then you go for PET CT immediately followed by CT guided biopsy or excision biopsy. So far we have been discussing about solid nodules. But there is another group which is called the sub-solid nodules. Sub-solid nodules are again of two types. One is part-solid nodule. Another is pure ground glass nodules. Why are sub-solid nodules important? Because the risk of malignancy is much more in sub-solid nodules. Look at that solid nodules 7 percent, part-solid nodules 63 percent and ground glass nodules 70 percent. So here is an example of a pure ground glass nodule. This is a part-solid nodule with a small solid component which cannot be picked up on the medistinal window and here is a nodule with a larger solid component which can be well seen in the medistinal window. There are quite a few different shields for a sub-solid nodules. One is hemorrhage, infection, organizing pneumonia, focal fibrosis. They all have the appearance of a sub-solid nodule. So adenocarcinomas of lung, which is 30 to 35 percent of primary lung tumors and the subset bronchoalveolar carcinoma commonly present as sub-solid nodules. The term bronchoalveolar carcinoma is now replaced by its histologic subtypes which has characteristic CT findings. So let us look at the histological subtypes. AAH, atypical adenomatous hyperplasia. What do we get in CT? Ground glass opacity which is less than equal to 0.5 centimeter. AIS or adenocarcinoma in C2. When we get a ground glass nodule which is more than 5 millimeter in diameter we are probably looking at adenocarcinoma in C2. There may be a small solid component along with it. MIA or minimally invasive adenocarcinoma. CT findings would be part solid nodule that is ground glass with less than 5 millimeter of solid component. And finally, invasive adenocarcinoma, non-mucinous or mucinous type where we get a part solid nodule which would be more than or equal to 5 millimeters or we get a solid nodule. So once we get these sub-solid nodules, what do we do with it? Freshness society again has certain recommendations. Recommendation one, a GGN which is less than 6 millimeters no follow-up is required. GGN which is more than 6 millimeters follow-up after 3 months then yearly follow-up every year for 5 years. And recommendation three for part solid nodules that consider malignant if it remains stable at 3 months and if it increases in size. If solid component is less than 6 millimeter likely to be AIS or MIA follow recommendation two which means we follow it up every year for 5 years. If solid component is more than 6 millimeter biopsy if not a surgical candidate. So what we need to know about nodules are majority of pulmonary nodules resolves at 3 months. Small and squamous cell carcinomas have faster growth rate than adenocarcinomas. And that is why the slow growing adenocarcinomas which presents as sub-solid nodules need to be followed up for 5 years. And finally the rationale for recommendation for serial follow-up studies is that some of them will turn out to be cancers and that early intervention will provide opportunities to cure. Thank you.