What does the "N" in the TNM system indicate?

The "N" in the TNM staging system specifically refers to regional lymph node involvement. This classification is crucial in determining the extent to which cancer has spread beyond the primary tumor site. The "N" category provides information about whether cancer cells have spread to nearby lymph nodes, which can significantly impact treatment decisions and prognosis.

In the TNM system, which stands for Tumor, Node, Metastasis, the assessment of lymph nodes helps oncologists gauge how aggressive the cancer may be and whether it has the potential to metastasize further. For instance, multiple affected lymph nodes or involvement of nodes that are located farther from the primary tumor can indicate a more advanced stage of cancer.

Other provided options do not align with the established definition of the "N" category within this system. Necrosis of the tumor does not directly inform about lymph node status, while nearby tumor growth is concerned with how the primary tumor itself expands. Nodal excision required is not a classification within the TNM system itself but may relate to treatment options depending on the patient's specific situation. Thus, regional lymph node involvement is the accurate and essential concept signified by the "N" in the TNM staging.