How is Ann Arbor Stage IV characterized?

Ann Arbor Stage IV is characterized by the involvement of multiple regions or organs beyond localized or single site disease. At this stage, the cancer has disseminated significantly, indicating it may be present in multiple anatomical sites, which can include both lymphatic and non-lymphatic tissues. The essence of Stage IV is that it represents an advanced progression of the disease, establishing that cancer cells have spread from their original site to various parts of the body, which marks a critical point in the classification of cancer severity and guides treatment decisions. Thus, identifying the multi-organ involvement is crucial for understanding the extent of the disease and planning appropriate therapeutic interventions.