Malignant lymphoma in adolescents and young adults: from the viewpoint of physicians.

Malignant lymphoma (ML) is one of the most common malignancies among adolescents and young adults (AYA), accounting for approximately 20% of newly diagnosed cancers in this group. Although Hodgkin lymphoma represents only approximately 4%-5% of all cancers in children younger than 15 years of age, its incidence increases to approximately 16% in AYA. In non-Hodgkin lymphoma, the common malignancies affecting AYA include diffuse large B-cell lymphoma, Burkitt lymphoma, and anaplastic large cell lymphoma. Although it is generally accepted that AYA with ML experience outcomes that are worse than those experienced by children with ML, there are several critical issues. Hemato-oncologists and pediatric oncologists often follow diverse treatment strategies for ML, and it is unclear as to which treatment strategy is more suitable for AYA. Considering other aspects, tumor biology may explain the different outcomes. In Japan, there are no detailed data regarding the incidence, biology, treatment, prognosis, and long-term outcomes of ML in AYA. In future clinical trials, it will be important to determine whether the different outcomes result from the differences between the therapeutic approaches in pediatric and adult regimens or they are attributable to other factors such as variation in tumor biology and aging.