Lymph node metastases. Indicators, but not governors of survival.

Regional lymph node filter function has traditionally been assumed to be critical in the prevention of the systemic spread of malignant cells shed from the primary cancer. However, in a multitude of clinical studies involving a variety of cancers, prophylactic removal of such regional lymph nodes, with or without metastases, does not improve cure rates compared with the observation of these lymph nodes. Furthermore, laboratory studies indicate that lymph node filter function may not be either complete or effective, and that many lymphatic and lymphaticovenous shunts exists that bypass regional lymph nodes and allow both lymphatic and hematogenous dissemination of malignant cells. These facts emphasize that regional lymph node metastases are indicators, but not governors, of survival in cancer. The timing of the clinical appearance of regional lymph node metastases and their number are, with few exceptions, excellent indicators of the biologic behavior of the primary cancer and the cells that are shed from it. This shedding of cells into the vascular and lymphatic vessels undoubtedly occurs simultaneously in the vast majority of cancers, but the later progressive growth of cells and micrometastases distributed hematogenously to vital organs is the ultimate governor of survival.