Blastomatous changes that develop in the lymph nodes affected by metastases of lung cancer, largely depend on the size of the metastasis and its histological structure. A serial histological examination of the lymph nodes removed during operations, carried out in the clinic, made it possible to establish with a high degree of certainty the frequency of such lesions and to determine the earliest, initial forms of lymph node lesions by metastases, which in these cases are usually presented as small-sized cancer cell complexes, more often total inaccessible to detection during standard histological studies in one or two sections of the preparations.
A detailed study of lymph nodes affected by metastases made it possible to trace the dynamics of growth and development of blastomatous changes in them. Getting with the lymphatic flow initially into the regional sinus of the lymph node, under its capsule, lung cancer metastasis begins its development here. The intermediate sinuses of the lymph nodes are much less likely to be the starting point for the formation and development of such tumor metastases.
Subsequently, metastasis, located subcapsularly, grows along the marginal sinus of the lymph node and spreads in the direction mainly inward, into the sinuses between the lymphatic follicles. Moreover, the nearby fibrous capsule of the lymph node remains unaffected or includes only small lymphoid infiltrates. Only when the lung cancer metastasis carries out all or almost all of the tissue of the lymph node, does it begin to grow beyond its fibrous capsule. Thus, regional lymph nodes fully provide the function of a kind of biological filters that prevent the spread of metastases, and their capsule for a long time serves as a kind of barrier, preventing the spread of the tumor. Therefore, the enlarged lymph nodes affected by lung cancer metastases closely adjacent to various anatomical structures of the lung and mediastinum, especially blood vessels, with an external impression of the spread of the tumor on their wall, they actually delimit, localize its local growth, accompanied only by the phenomena of non-specific periadenitis and can be removed with surgical intervention.
The defeat of the regional lymphatic apparatus of the lungs by metastases has peculiar features depending on the degree of differentiation of the cell structure of lung cancer.
In highly differentiated cancers, the detection of a single metastasis of a tumor or several metastases of various sizes — from very small to large — is most common during a regional lymphatic collector. Such size differences indicate a sequential, in several stages, the entry of malignant cells from the primary tumor into the lymphatic channel, often with long time intervals.
Undifferentiated cancer is characterized by a simultaneous, wide, avalanche-like penetration of metastases into the network of lymphatic capillaries and blood vessels. Moreover, in regional and even more distant groups of lymph nodes, multiple metastases and all of approximately the same size are most often found: either all are small, or — sufficiently large, i.e. approximately the same terms of formation, development and growth. This fully reflects the high degree of biological malignancy and invasiveness of lung cancer of an undifferentiated structure.