Time trends in rates of Hodgkin lymphoma histologic subtypes: true incidence changes or evolving diagnostic practice?

Conclusions of study: Recent nodular sclerosis rate declines largely represent true incidence changes. Long-term rate decreases for mixed cellularity and other less-common subtypes, and increases for NOS (comprising approx 30% of cHL cases in 2011), likely reflect changes in diagnostic and/or classification practice. Impact: Diminishing histologic subtyping undermines future surveillance and epidemiologic study of HL. Guideline-based use of excisional biopsies and more coding quality control are warranted.