Risk of familial classical Hodgkin lymphoma by relationship, histology, age, and sex: A joint study from five Nordic countries.
The rarity of familial Hodgkin lymphoma (HL) has hampered detailed analyses of familial clustering. We aimed to provide the familial risk of HL by relationship, histology, age at diagnosis and sex. A cohort of 57,475 first-degree relatives of 13,922 HL patients, diagnosed between 1955 and 2009, in five European countries was followed for HL incidence. Standardized incidence ratios (SIRs) were calc