In which Ann Arbor stage are lymph nodes on both sides of the diaphragm involved?

Lymph node involvement on both sides of the diaphragm is characteristic of Stage III in the Ann Arbor staging system for lymphoma. In this stage, the disease is more advanced than in earlier stages, where lymph node involvement is typically confined to a single region or one side of the diaphragm. Stage III indicates that multiple lymph node regions are affected, which can include nodes in the cervical, axillary, mediastinal, abdominal, and pelvic areas, crossing the diaphragm to involve both thoracic and abdominal nodes. This bilateral involvement signifies a systemic rather than localized disease, highlighting a critical distinction in lymphoma staging and helping to guide treatment decisions.