According to the Ann Arbor classification system, what stage is indicated by a patient having lymph node involvement on both sides of the diaphragm?

The correct answer is indeed that the patient is classified under Stage III in the Ann Arbor classification system. In this system, Stage III indicates that the lymphoma has spread to lymph nodes on both sides of the diaphragm. This distinction is crucial as it signifies a more advanced disease state than earlier stages, where the spread is usually localized to one side of the diaphragm or to a single region of lymph nodes.

At Stage III, the involvement of bilateral lymph nodes means that the disease has progressed, demonstrating the importance of staging in determining treatment plans and prognoses for patients. This classification helps healthcare professionals assess the extent of the disease and make informed decisions regarding management.