What is considered nonregional when discussing nodes outside the regional nodes?

When discussing nonregional nodes in the context of oncology and lymphatic spread of cancer, the retroperitoneal nodes are classified as nonregional. This is primarily because they are not located in the immediate area related to certain primary tumors or their typical routes of metastasis.

Regional nodes are those lymph nodes that are closest to a specific primary tumor, which are the first ones to be affected by potential lymphatic spread of disease. For example, retroperitoneal nodes are located in a different anatomical region than the primary tumor sites for many cancers, such as those of the pelvis or abdomen. Their involvement may suggest a more advanced stage of disease and indicate dissemination beyond the local or regional lymphatic areas.

In contrast, pelvic and abdominal nodes are generally considered regional to tumors in those respective areas because they are more likely to be directly involved in metastatic processes from primary tumors located in the pelvis or abdominal cavity. Lymphatic drainage nodes, as a category, do not specifically denote an anatomical group that would consistently fit the description of nonregional either.