Again, the size of the lung nodule is important, and the differential diagnosis of small nodules less than 3 cm is essential, because even if they are tumors, most of them still belong to the curable stage. As in all industries, experts always like to give a mysterious moniker to something very simple, which provides convenience to the layman to imitate the insider’s speech, but more importantly, it serves to unify the concept for scientific research. In this context, the medical community has given the scientific name SPN to pulmonary occlusions smaller than 3 cm, which refers to a single peripheral type of round or round-like lesion <= 3 cm in diameter in the lung, completely surrounded by lung tissue and not accompanied by other lesions such as pneumonia or atelectasis. The definition is long, and I like to summarize its characteristics in 4S: Single: solitary; Spherical: spherical; Scribed-circumscribed: well-defined; Surrounded: surrounded by lung tissue. There is also a more specific name of GGO, hairy glass nodule. I personally have reservations about including GGO in the SPN category, because GGO and substantial nodules are very different in terms of probability of malignancy, follow-up, surgical options, and pathologic findings, and should be treated separately. I often interpret pure hairy glass lesions as a balloon with a layer of oil on the surface, where the balloon represents a normal alveolus and the oil is like a layer (note the single layer) of tumor cells. The resulting presentation on CT is as blurry as the hairy glass on your bathroom, with a kind of hazy beauty (provided of course that the person taking the shower is in good shape), which is very different from the meatball-like solid nodules, not only at the aesthetic level, but also with a much better prognosis, because many GGO are carcinomas in situ or microinvasive. The professor says: the new lung adenocarcinoma staging defines a single layer of cancer cells that does not break through the basement membrane as carcinoma in situ. Tudor explanation: It is that layer of oil can only wiggle on the surface of the balloon, it has nothing to do with the balloon, it will fall off as soon as you touch it if you want. Professor says: Tumors that invade through the basement membrane <5mm are defined as microinvasive carcinoma. Tuohy explained: too much grease, it becomes several layers and penetrates inside the balloon wall, it is hard to put it off, it is serious. I said it is okay, the cure rate of both in situ cancer and microinvasive cancer is 100%. More than 5mm becomes invasive cancer, even if radical surgery is performed, without lymph node metastasis, the cure rate is about 85%.