In the AJCC TNM staging framework, the 'N' component refers to what?

• A. Neural invasion
• B. Number of nodal metastases
• C. Extent of regional lymph node involvement
• D. Negative surgical margins

Answer: (C)

In the AJCC TNM system, the N component describes the extent of regional lymph node involvement. This reflects how far the cancer has spread to nearby lymph nodes—considering not just how many nodes are affected, but also their size, exact location, and whether disease extends outside the nodes (extranodal extension). This information helps predict prognosis and guide treatment decisions.

It's not about neural invasion, which is a separate histopathology feature (often called perineural invasion), and it's not about whether surgical margins are free of tumor—that status is captured as margins or R status, not N. While the number of affected nodes can influence N category, the core idea is the overall pattern and degree of nodal spread near the primary tumor.