A variety of cause-and-effect relationships, features of the biology of a cancerous tumor, differences in its cellular structure and vital functions of a sick person determine a wide range of hematogenous metastasis of lung cancer. Often it is very individual: from an extensive lesion to a limited, local development of hematogenous metastasis, the only tumor site outside the lung.
Morphological changes observed in metastasis developing in the affected organ are peculiar and may slightly differ from the primary tumor in the lung. The histological structure of metastasis most often repeats the structure of the neoplasm that caused its appearance, but it can also differ from it, especially when it comes to polymorphic cancer, which metastases one of the cellular components of its constituent. Then it is possible to observe a decrease or increase in the differentiation of the tumor in its metastasis, and its development in its characteristics will more closely correspond to its cellular structure.
Highly differentiated lung cancers are less likely to metastasize not only by the lymphogenous, but also by the hematogenous route. In these cases, damage to the internal organs, if it occurred, is usually represented by a single, solitary metastasis.
Undifferentiated forms of lung cancer, on the contrary, metastasize more often and more extensively, and their spread through the blood vessels is characterized by the multiplicity of its manifestations. Often there is an intense, approaching in size to the primary tumor in the lung, an increase in the volume of hematogenous metastases of undifferentiated cancer. In small cell lung cancers, such a development of metastases sometimes even outstrips the growth of the primary tumor.
Morphological features of the structure and structure of solitary hematogenous metastases of lung cancer are most thoroughly studied during their development in the brain. Some general morphological features of their growth manifest themselves quite similarly in the case of damage to other organs.
The metastatic focus of tumor development manifests itself in the form of progressive local growth with displacement, destruction and replacement of the tissue of the affected organ. Sometimes the formation of a “capsule” around the metastasis in the affected area of its growth is most often not detected. The tumor in the form of short outgrowths, tongues and layers of malignant tissue spreads along the perivasal and interstitial gaps.
The destruction of blood vessels often leads to trophic disorders and necrosis, the melting of the central part of the largest solitary metastases.
With the development of hematogenous metastasis in an organ that has a well-developed lymphatic system — often in the opposite lung — the spread of tumor cells from metastasis through the lymphatic collectors is possible. Such lymphogenous metastases arising from solitary hematogenous metastasis in one of the organs are not very often figuratively called them “granddaughter metastases” in relation to the primary tumor in the lung.
Targeted postmortem examination and clinical observations suggest that by the time of recognition of lung cancer, hematogenous metastases can be established in 6% of patients. This indicator reaches the highest values with lung cancer with metastases to regional lymphatic collectors. Among lung cancer patients who underwent radical surgery and died in subsequent years from hematogenous metastases, in 30% of cases, the cause of death was the progressive development of solitary metastasis, most often quite accessible to surgical removal in an earlier period. Therefore, for some patients with lung cancer, such a solution to the issues of therapeutic tactics seems quite reasonable.
In general, the solitary metastases of lung cancer in morphological structure, the features of their growth and development are more close to an independent malignant tumor. This should be taken into account when planning and performing their surgical removal within cancer limits.