Scientific analysis of the diagnosis of lung metastasis

In recent years, more and more people have been threatened by tumors, and lung metastasis has become one of the high-incidence areas in my country. The early symptoms of lung metastasis are not obvious, and usually symptoms are in the middle and late stages. So how do we diagnose lung metastasis? The diagnosis of lung metastasis mainly includes two aspects:

1. Pulmonary metastases with special manifestations should be differentiated from the following diseases:

1. Staphylococcus aureus pneumonia: It is characterized by rapid onset, severe clinical symptoms, high fever, and the primary manifestations of pneumocystis and air-fluid level. Follow-up observation shows rapid changes in the condition.

2. Tuberculoma: often solitary, cavitary, and thick-walled fissure-like, with localized arc-shaped, annular or diffuse spot-like calcification. There are often cord-like shadows connected to the hilum of the lung, and satellite lesions in the nearby lung fields.

3. Cystic bronchiectasis: Hemoptysis is common, and the lesions are distributed along the bronchi, appearing like a bunch of grapes, with typical manifestations.

4. Pulmonary mycosis: There are no characteristic manifestations, and it is difficult to differentiate from pulmonary metastasis. It needs to be confirmed by combining clinical history or sputum examination. When the lesion shows the typical air crescent sign, the lesion is already in the middle or late stage or absorption stage.

2. Atypical lung metastases are often encountered in clinical practice and need to be differentiated from other non-malignant lung diseases:

The radiological manifestations of atypical pulmonary metastases include: cavitation, calcification, peritumoral hemorrhage, pneumothorax, air-filled space lesions, tumor embolism, endobronchial metastasis, solitary metastasis, intratumoral vascular dilation, sterilized metastases, and benign tumor pulmonary metastases.

1. Hollow

Cavities are rare, accounting for only 4%, which is lower than the incidence of primary lung cancer (9%), of which 70% are metastases from squamous cell carcinoma. However, recent studies have shown that there is no significant difference in the incidence of cavitary metastasis between adenocarcinoma and squamous cell carcinoma on CT. In addition, metastatic sarcomas can also develop cavities, accompanied by pneumothorax. Chemotherapy can also lead to cavitation. The mechanism of cavitation is often difficult to determine, and it is generally believed to be caused by tumor necrosis or invasion into the bronchus to form valves. Cavities are more common with irregular thick walls, and lung metastases of sarcoma or adenocarcinoma may be thin-walled cavities. Sarcoma metastasis may be accompanied by cavities, but is often accompanied by pneumothorax.

2. Calcification

Calcification of pulmonary nodules often indicates benign disease, most commonly in granulomatous lesions, followed by hamartomas. However, calcification or ossification may also occur in metastatic nodules of some malignant tumors in the lungs, which can be seen in osteosarcoma, chondrosarcoma, synovial sarcoma, giant cell tumor of bone, lung metastasis of colon cancer, ovarian cancer, breast cancer, thyroid cancer, and treated metastatic choriocarcinoma. Calcification mechanisms include: A bone formation (osteosarcoma or chondrosarcoma). B dystrophic calcification (papillary thyroid carcinoma, giant cell tumor of bone, synovial sarcoma, or treated metastatic tumors). C mucinous calcification (gastrointestinal and breast mucinous adenocarcinoma). CT is an accurate method for detecting calcification, but it cannot distinguish calcification in metastatic nodules from granulomatous lesions or hamartomas.

3. Peritumoral bleeding

The more typical CT manifestation is the appearance of ground-glass density or halo with blurred edges (halo sign) around the nodules. However, the halo sign is not specific and can also be seen in other diseases, such as invasive aspergillosis, candidiasis, Wegener's granulomatosis, tuberculoma with hemoptysis, bronchioloalveolar carcinoma and lymphoma. The chest X-ray shows multiple nodules with irregular edges. Pulmonary metastases of angiosarcoma and choriocarcinoma are most prone to bleeding, probably because the walls of the new blood vessels are fragile and easy to rupture.

4. Pulmonary metastases are prone to pneumothorax

Spontaneous pneumothorax is rare. Literature reports that lung metastasis of osteosarcoma is most likely to be complicated by pneumothorax, which occurs in 5% to 7% of cases. Pneumothorax has also been reported in other sarcomas or malignant tumors that are prone to necrosis. The mechanism of occurrence may be due to necrosis of subpleural metastases and formation of bronchopleural fistula. Patients with osteosarcoma should be highly alert to lung metastasis when pneumothorax occurs.

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