[Pathological features of lymph node metastasis. 2) From morphological aspects].

Lymph node metastasis is important because of its early appearance and prognostic significance. In this paper the mechanism of development of metastasis, tissue reaction with metastatic cells, and role of lymph node metastasis in cancer spread are described briefly. Lymph node metastasis proceeds when cancer cells invade lymphatic vessels. These cells lodge in the lymphatic sinus where tumor cells adhere to and breach the sinusoidal walls and migrate into the parenchyma. Integrin(s), CD44, and/or carbohydrates of tumor cells and extracellular matrix components such as laminin and type IV collagen, hyaluronic acid, and lectins of the sinus wall become involved in the adherence of cancer cells. Their binding may induce matrix metalloproteinase production from cancer cells, resulting in degradation of surrounding reticular fibers. Lymph nodes sometimes react with tumors, exhibiting follicular hyperplasia, sinus histiocytosis, lymphoid cell depletion, fibrosis, and angiogenesis of lymph nodes. Such tissue reactions may suppress cancer spread but in turn may augment the aggressiveness of cancer cells. It is not yet possible to determine which reaction will occur. In early cancer, lymph node metastasis occurs based on mainly anatomical-mechanical factor, while in advanced cancer, seed-soil factor plays an important role on development of the metastasis.