[The frequency of malignant lymphoma subtypes based on World Health Organization (WHO) classification].

Diagnosis of malignant lymphoma is based on the 4th edition of World Health Organization (WHO) Classification of Tumours of Haematopoietic and Lymphoid Tissues. The frequency of malignant lymphoma subtypes depends on age, race and geography. In Asian countries, Hodgkin lymphoma and follicular lymphoma are less frequent compared to Western countries. However, the number of patients with follicular lymphoma is now increasing in Japan. In contrast, in Japan, adult T-cell leukemia/lymphoma is more frequent than in Western and other Asian countries, because it relates to distribution of human T-cell leukemia virus type 1(HTLV-1).