Four ways of metastasis of lung metastases

1. Hematogenous metastasis

Hematogenous metastasis of lung metastases is the most common, and hematogenous metastasis occurs when tumor cells pass through the vena cava. Returns to the right heart and transfers to the lungs. After the tumor thrombus reaches the pulmonary arterioles and capillaries, it can infiltrate and penetrate the blood vessel wall, grow in the surrounding interstitium and alveoli, expand and compress the surrounding lung tissue to form a well-defined round mass, and form pulmonary metastases.

The most common form of hematogenous metastasis is multiple nodules or masses. Various malignant tumors can show this typical sign. If there is a history of primary tumors, it is not difficult to make a diagnosis. Single nodule type is more common in the periphery of the middle and lower lung fields. The nodule has a clear outline and is difficult to differentiate from peripheral lung cancer when it is lobulated.

2. Lymphatic metastasis

Lymphatic metastasis mostly transfers from the blood to the interstitium around the pulmonary arterioles and capillaries, the interlobular interstitium and the subpleural interstitium, and then travels through the lymphatic vessels in the lungs. Spread within. Tumor cells can also infiltrate into capillaries and then penetrate the blood vessel wall to invade the peribronchial and vascular lymph nodes, grow substantially, and form swollen lymph nodes, or dilate lymphatic vessels to form strips, fine meshes, and other changes through lymphatic infiltration and lymphatic embolism. Impaired lymphatic drainage can lead to pleural effusion.

Lymphatic metastasis is characterized by cancerous lymphangitis and lymph node enlargement, mostly from tumors of the digestive tract, lungs, breasts and female reproductive system.

HRCT shows thickening of the bronchovascular bundles with nodules, bead-like changes or thickening of interlobular septa, nodular foci in the center of the lobules, subpleural nodules, and possibly hilar Lymph node enlargement is mainly unilateral, more common on the right side.

3. Airway metastasis

Airway metastasis is defined as the discontinuous spread of cancer cells from the primary tumor to adjacent or distal lung parenchyma through the airways.

CT signs suggesting airway metastasis include: multiple centrilobular nodules, blurred branches showing a tree-in-bud sign, usually unclear borders, and ground-glass shadows visible. Well-circumscribed soft tissue nodules are rare. The nodules formed by airway dissemination are distributed in clusters, and signs of enlargement of the nodules can be seen. These nodules can fuse to form cavities. When metastases are far away from the primary tumor, the nodules formed are mostly distributed in the lower parts of the lung lobes.

When persistent or gradually growing centrilobular nodules are found on CT in patients with lung adenocarcinoma, the possibility of airway metastasis should be considered, especially when these nodules are accompanied by erosive, Mucinous, papillary or micropapillary type. Some small cell carcinomas can also metastasize through the airways.

Airway metastasis generally grows faster and is not sensitive to chemotherapy.

4. Direct spread

Malignant tumors in the mediastinum, pleura and chest wall can spread directly to the lungs, manifesting as metastases of varying sizes. CT and MRI can show the relationship between metastases in the lungs and the primary tumor and the invasion of the ribs and pleura.

When metastatic lung tumors are small, symptoms rarely occur, especially blood metastasis, and blood in coughs and sputum is rare. Shortness of breath may occur with large amounts of pulmonary metastasis, especially lymphatic metastasis. When pleural metastasis occurs, there may be chest tightness or pain. Metastatic tumors in the lungs change rapidly, and the tumors can be enlarged or multiplied in a short period of time; some can shrink or disappear after the primary tumor is removed or after radiotherapy or chemotherapy.