NCIt definition : A coding system for staging of cancer bringing together the principles of Summary
Stage, the TNM categories and stage groupings, and the SEER Extent of Disease (EOD)
coding structure, creating a carefully selected set of data items that describe how
far a cancer has spread at the time of diagnosis. The Collaborative Staging System
uses a modified EOD coding system, a five-field, 10 digit system: tumor size (3 digits),
extension of the primary tumor (2 digits), regional lymph node involvement (highest
specific lymph node chain involved by tumor) (1 digit), the number of pathologically
reviewed regional lymph nodes that are positive (2 digits), and the number of pathologically
examined regional lymph nodes (2 digits).;