Ground glass, also known as "frosted glass", refers to translucent glass with a rough surface that has been ground with emery or chemically treated. The name of the pulmonary ground glass nodule uses the familiar ground glass to vividly describe the appearance of this type of lung nodule. On CT chest, images of ground glass nodules in the lungs resemble ground glass, showing cloud-like round, circular lesions, or irregular shadows.
Pulmonary nodules are defined as focal, rounded, densely dense, or sub-solid irregular shadows of the lungs with a diameter of ≤3 cm in diameter in medical imaging, which may be isolated or multiple, and are not accompanied by atelectasis, hilar lymphadenopathy, and pleural effusions.
It can be seen that the pulmonary ground glass nodule is a kind of lung nodule divided according to density, which belongs to the category of sub-solid nodules. If the density within the nodule lesion is low and uniform, there is no high density of solid components, and the blood vessels and bronchi in the nodule are not covered, it is called a pure ground glass nodule. If there is a high density of solid components inside the lesion, the density is uneven, and the blood vessels and bronchi are partially obscured, it is called a mixed ground glass nodule.
Why talk about "ground glass" discoloration
A polished glass nodule in the lungs is an imaging manifestation based on a change in density, and any change in the degree of inflation of the alveolar cavity can form a ground glass nodule on CT images. That is to say, the ground glass nodule is only an objective description of imaging, and does not represent the disease itself or indicate the direction of the disease.
So why are so many people afraid of talking about ground glass nodules in the lungs? The reason is that some of the ground glass nodules in the lungs develop early lung cancer.
"Ground glass" has good and bad
Pulmonary ground glass nodules have benign lesions and malignant tumors. Benign lesions include lung inflammation, fungal infections, charcoal deposition, etc., and malignant lesions are lung adenocarcinoma.
Lung adenocarcinoma is divided into pre-invasive stage, micro-invasive adenocarcinoma and invasive adenocarcinoma, which generally grows gradually. It is worth mentioning that the pre-invasion phase includes atypical adenomatous hyperplasia and carcinoma in situ. The former has been classified as a benign stage, and the World Health Organization's latest classification of thoracic tumors has removed carcinoma in situ from lung cancer as a benign lesion.
Benign ground glass nodules (mostly infectious) can shrink and disappear within a certain period of time (1 to 12 months, or even longer), so benign pulmonary ground glass nodules do not need to be operated.
Long-term and persistent, ground glass nodules in the lungs with an increased proportion of solid components increase the probability of malignancy and are thought to be an inert subtype of lung adenocarcinoma, generally slow-growing and highly occurring in East Asian populations, with mostly non-smoking women.
What to do if there is "ground glass"
If it is a pulmonary terrazzo found on the first chest CT examination, the international general trend is to regularly review the chest CT as the main means, and surgical intervention is not recommended. Surgery may be considered if multiple ct scans of the chest are followed up, suggesting an enlarged nodule or an increased solid proportion. In particular, surgery is recommended when imaging suggests that there may be micro-invasive adenocarcinoma or invasive adenocarcinoma. If imaging suggests atypical adenomatous hyperplasia or carcinoma in situ, regular follow-up of chest CT follow-up is recommended to dynamically observe changes.
Generally pure ground glass nodules below 10 mm or even below 20 mm, foreign guides recommend follow-up observation. The reason is that tumor pure ground glass nodules (clinically excluding inflammation, tuberculosis, fungal infection, charcoal deposition and other non-neoplastic possibilities) are mostly carcinomas in situ and micro-invasive adenocarcinomas. If removed in time, the five-year survival rate is almost 100 percent.
Surgical surgery for a tumoric pulmonary ground glass nodule depends on the pathological stage of the nodule. If it is a small invasive adenocarcinoma, invasive adenocarcinoma, surgery is recommended; if the carcinoma in situ is more than 8 mm, the patient's psychological pressure is large, and the three conditions are satisfied, surgery can also be performed; if it is atypical adenomatous hyperplasia, it is recommended to follow up on REGULAR CT and dynamically observe.
Whether a patient chooses a surgical option or a regular CT follow-up depends on three things: First of all, fully understand the imaging characteristics of benign and malignant nodules, the law and controversy of tumor metastasis. Second, fully understand the meaning of scientific uncertainty, critically study various guidelines and literature, and learn to accept scientific uncertainty. Finally, fully recognize the current medical humanistic environment in China, think in a different position, and recognize the harmonious relationship between doctors and patients.
In fact, tumoric lung terrazzo nodules are inert lesions that develop slowly, often showing a "turtle rate" of 1 to 2 mm in 3 to 5 years. This greatly prolongs the window period for patients with ground glass nodules in the lungs to choose surgery.
There are large individual differences in the growth rate and degree of malignancy of pulmonary ground glass nodules, and the cause is not clear. For nodules that cannot identify the pathological stage, it is recommended to follow up regularly to observe CT and dynamically see the changes. If there is a change in size, form, or density, please consult a doctor in time.
Doctor-patient decision-making is important
At present, there are blind spots in medicine, such as confusion about the causes of rapid growth of some ground glass nodules, confusion about whether multiple pulmonary ground glass nodules are primary or metastatic. The reality is that we are all like blind people, trying to portray an entity that we cannot observe completely.
We must be careful not to overemphasize a particular point of view or deliberately draw conclusions from specific observations. Patients need to communicate adequately with their doctors to make the choice that is most beneficial to them.
All in all, it is crucial for doctors to infer the nature of pathology from images. Even if the doctor infers that the malignancy is some, some of them are inert tumors, most of which develop slowly and have a low probability of metastasis.
The choice between CT follow-up or surgical resection has become a philosophical question of combining objective and subjective. Joint decision-making between doctors and patients is an effective means to solve such confusions.
Text: Zhao Xiaogang, Department of Thoracic Surgery, Shanghai Pulmonary Hospital
Editor: Zhang Fangfei Luan Zhaolin
Review: Xu Bingnan Yan Gong