Stephen M. Ansell, MD, PhD, a professor of medicine, chair of the Division of Hematology, co-leader of the Hematological Malignancies Program, and interim chair of the Department of Oncology at Mayo Clinic. explains the importance of making an accurate diagnosis of Hodgkin lymphoma. He highlights why needle biopsies may not always be reliable due to the low number of cancer cells in the tumor, and emphasizes the role of excisional biopsies. Dr. Ansell also discusses the value of expert pathology and the use of CD30, PDL1, and PDL2 staining, which support both diagnosis and treatment planning.