Among classical Hodgkin lymphoma (cHL) histologic subtypes, recent declines in nodular sclerosis (NS) rates largely represent true incidence changes. Long-term rate decreases for mixed cellularity (MC) and other less-common subtypes, and rate increases for not otherwise specified (NOS), likely reflect changes in diagnostic and/or classification practice. This according to a study of 21,272 patients with Hodgkin lymphoma. Researchers found:

• cHL rates were stable until 2007, then decreased for whites.

• NS rates decline after 2007 by 5.9%/year, with variation by gender, age, and race/ethnicity.

• During 1992 to 2011, MC rates declined and NOS rates rose overall and in most patient groups.

• During 2007 to 2011, NOS age-specific rates were more similar to MC rates for 1992 to 1996 than 2007 to 2011.

• Trends in combined rates were minimal, supporting increased misclassification of MC, LD, and specific NS subtypes as NOS.

Citation: Glaser SL, Clarke CA, Keegan TH, Chang ET, Weisenburger DD. Time trends in rates of Hodgkin lymphoma histologic subtypes: true incidence changes or evolving diagnostic practice? [Published online ahead of print July 27, 2015]. Cancer Epidemiol Biomarkers Prev. doi: 10.1158/1055-9965.EPI-15-0281.