The medical community has confirmed that chest fluoroscopy and X-rays are not effective in detecting early stage lung cancer. In recent years, with the promotion of medical checkups and the widespread use of chest CT, more and more “patients” have been found to have nodules in their lungs. However, although some of the lung nodules found in medical checkups are indeed early-stage lung cancer, many of them are also benign lesions.
So, how do you know if your nodule is lung cancer or just a “false alarm”? It starts with how a potentially “bad” nodule turns into lung cancer step by step.
“Ground glass nodule”: Is it always lung cancer?
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Early-stage lung cancer detected by CT is usually peripheral lung cancer, and the pathologic classification is usually adenocarcinoma of the lung in non-small cell lung cancer (NSCLC). If we want to understand whether a lung nodule is benign or malignant, we have to understand the basic process of early lung adenocarcinoma evolution first.
Simply put, the development of peripheral lung adenocarcinoma is a dynamic process from a “false” ground glass nodule, to a partially solid ground glass nodule, and then to a completely solid nodule on CT.
If we compare the lung to a building, the alveoli are the basic units of gas exchange. The precursor of peripheral adenocarcinoma is atypical adenomatous hyperplasia (AAH). At this stage, the cells are often dormant for a long time, and the alveolar cells are hyperplastic (but not malignant) and the alveolar wall is thickened, but the alveolar cavity is still filled with gas. At this stage, the lesion is not a solid nodule, but a faintly increasing shadow called a ground glass opacity (GGO).
When these proliferating cells become malignant, the lesion becomes an early stage lung cancer. In the earliest stage, the cancer cells remain in the alveoli and can only spread through the small holes that naturally exist between the alveoli, and cannot infiltrate or destroy the surrounding tissues. This stage of lung cancer is called bronchioloalveolar carcinoma (BAC), which is a kind of in situ cancer without the ability to invade and metastasize, and the cell growth is also very slow. Therefore, at this stage, the alveoli are still not completely filled with tumor cells, and the nodules seen on CT are still ground glass nodules and often remain stable for a long time.
As the tumor cells grow, the alveolar cavity will gradually fill up and become a solid lesion; and the tumor will destroy the normal tissue structure and begin to metastasize and spread, developing into an aggressive adenocarcinoma. At this stage, the tumor grows rapidly and is observed as a solid nodule on CT, and the nodule will be found to be increasing in size during the follow-up.
Understanding the above process, we know how the doctor comes to determine the nature of the lung nodule. Yes, it is to analyze the morphologic features of the lesion on CT images and follow up to track the dynamic changes of the lesion.
Small nodules on the lungs, what to do?
We refer to lung lesions smaller than 3 cm detected on CT as nodules, of which those smaller than 1 cm are called small nodules. It is generally accepted that nodules smaller than 5 mm are difficult to diagnose and are mainly observed for follow-up.
Depending on their nature, nodules can be subdivided into pure ground glass nodules, partially solid ground glass nodules, and solid nodules. We describe the management of these three types of nodules separately.
1. Pure ground glass nodule
It may be a benign lesion, precancerous lesion, or carcinoma in situ. However, at this stage, even if it is malignant, it does not have the ability to invade and metastasize.
Therefore, the standard management process is to follow up with regular CT examinations. Usually a plain CT scan is sufficient, and if available, a thin-section scan or 3D reconstruction analysis can be done.
It should be noted that enhanced CT and PET-CT scans are not meaningful. This is because the number of tumor cells in the lesion is small and the cells have not entered into the vigorous growth stage, so the PET-CT results are often “normal” and cannot exclude the possibility of malignancy.
During the follow-up, if the lesion is obviously reduced or absorbed, malignant tumor can be basically ruled out; if the lesion has a tendency to increase dynamically or increase in density, further examination or even surgical resection can be considered; if the lesion remains stable, long-term follow-up is required, usually more than 3 years in a row, but it is still uncertain how long follow-up is needed to rule out the possibility of tumor. The doctor will make a specific follow-up plan according to the relevant guidelines.
2. Partially solid ground glass nodules
At this stage, if it is an early stage tumor, the growth activity is significantly enhanced.
If a benign lesion cannot be confirmed by other methods, it needs to be closely observed and followed up. The physician may use methods such as puncture to obtain specimens for appropriate lesions to confirm the diagnosis.
During follow-up, if there is a dynamic increase in the extent and density of the lesion, more consideration needs to be given to aggressive surgical treatment.
3. Solid nodules
If the nodule on CT shows burriness, lobulation, unclear borders, irregular margins, inhomogeneous density, distorted surrounding vessels, bronchial inflations within, and thick-walled cavities, these are signs of malignancy. On the contrary, calcification, thin-walled cavities with shiny borders, regular morphology, uniform density, and smooth inner walls are benign signs. If necessary, enhanced CT and PET-CT can also help determine the nature of the lesion.
For lesions whose nature cannot be determined, dynamic observation of its growth trend is a more feasible method. A lesion that grows rapidly in a short period of time or remains stable for a long time may be relatively less malignant; a lesion that maintains a certain rate of continuous growth may be more malignant. For lesions where lung cancer is suspected or where the nature needs to be determined as soon as possible, doctors can help diagnose through bronchoscopy, puncture or surgical biopsy.
Along with imaging, the doctor will also take a detailed history, do physical exams, blood tests, diagnostic treatments, and other traditional diagnostic techniques.
Which nodules need to be removed?
Chest CT does find a lot of early lung cancer and saves lives as a result, but it also leads to unnecessary surgery for some “patients.
Surgery is a relatively expensive, invasive, and risky procedure that causes irreversible damage to lung function. Therefore, the timing of surgery for pulmonary nodules should always be determined in full consultation with the surgeon.
Usually, it is more appropriate to operate if the lesion is located in the center of the lobe and the area to be resected is large and followed until the nature is clearer; if the lesion is located in the periphery, the scope of surgery is small, the person is very eager to deal with it aggressively, and the doctor suspects malignancy, aggressive surgery is not uncommon.
To sum up, CT examination reveals small nodules in the lung, which increases the chance of early detection of lung cancer, but not all nodules are lung cancer. You don’t need to be anxious, just cooperate with your doctor, treat and follow up as planned. If you have no bad habits, there is no need to change your original rhythm of life. After all, a good mind and healthy lifestyle are the best way to prevent and fight cancer.
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Co-reviewed by: Guangdong Provincial People’s Hospital Guangdong Lung Cancer Research Institute Dr. Dong Song, Associate Chief Physician Dr. Zhang Chao