Introduction

This issue of International Journal of Hematology presents four review articles relating to “Progress in Hematology” (PIH).

Malignant lymphoma (lymphoma) is the most common hematological malignancy; however, the term “lymphoma” encompasses a heterogenous group of biologically and clinically distinct neoplasms. Lymphoma originates from lymphoid cells and is divided into B-cell lymphoma, T/NK (natural killer)-cell lymphoma and Hodgkin’s lymphoma (HL). More than 90 subtypes of lymphoma, including provisional types, are listed in the World Health Organization (WHO) classification [1]. Advances in molecular biology and immunology have revealed important issues about the molecular mechanisms underlying lymphomagenesis and the prognosis of lymphoma.

The World Cancer Report 2014 stated that there were almost 566,000 new lymphoma patients worldwide in 2012, and about 305,000 deaths from the disease [2]. Globally, the incidence of non-Hodgkin’s lymphoma (NHL) is 6.0/100,000 population among males and 4.1/100,000 population among females. The mortality rate of NHL is 3.2/100,000 population among males and 2.0/100,000 population among females [2]. The number of lymphoma patients is increasing year by year around the world as well as in Japan [2, 3] (Fig. 1). The incidence of lymphoma is higher in Western countries than in Asian countries (Fig. 2) [2]. Furthermore, there are geographic variations in the frequencies of each lymphoma subtype [1]. In a study of 2260 Japanese lymphoma patients conducted between 2001 and 2006, it was reported that diffuse large B-cell lymphoma (DLBCL) accounted for 33% of cases, and follicular lymphoma (FL) and adult T-cell leukemia-lymphoma (ATL) accounted for 18% and 10% of cases, respectively [4]. In a study of 4638 Chinese lymphoma patients conducted between 2004 and 2008, DLBCL was the most common subtype of lymphoma, accounting for 36% of cases, which was similar to its frequency in the Japanese study. Extra-nodal NK-cell lymphoma, nasal type (ENKL) accounted for 11% of cases [5], which was higher than its frequency in the Japanese study, while the incidence of FL was 3%, and ATL was only seen in one patient [5]. A study that analyzed 5318 Korean lymphoma patients showed that the incidence rates of DLBCL, ENKL, and marginal zone lymphoma were 31, 3.9, and 12%, respectively. There was also only one ATL patient in this series [6]. Thus, the frequencies of lymphoma subtypes differ among Asian countries. We might be able to obtain clues about lymphomagenesis by comparing and examining the data for each Asian country (Fig. 3).

Fig. 1
figure 1

Age-standardized (global) incidence rates of lymphoma in males per 100,000 population by year in selected populations from circa 1975–2012 (Ref. [2])

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Fig. 2
figure 2

Incidence rates and trends for hematological malignancies from 1993 to 2008 in Japan and the US. Data for the US are shown in red, and data for Japan are shown in blue. The circles indicate the observed age-standardized incidence rates of males and females combined, and the lines indicate the age-standardized incidence rates estimated by Joinpoint regression analysis. The Y-axis shows the annual incidence per 100,000 population (Ref. [3])

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Fig. 3
figure 3

Global distribution of estimated age-standardized (global) incidence rates (ASR) of lymphoma in males per 100,000 population in 2012 (Ref. [2])

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We searched PubMed for papers that were written in English and published in or after 1998 (a 20-year period) using the terms “lymphoma” and “Japan”, “Korea”, “China”, or “Singapore”. In Japan, 2248 relevant papers were published between 1998 and 2002, 2213 were published between 2003 and 2007, 2453 were published between 2008 and 2012, and 3485 were published between 2013 and the present day. In Korea, 230 (1998–2002), 452 (2003–2007), 783 (2008–2012), and 1453 (2013–present) relevant papers were published in these periods. In China, 208 (1998–2002), 438 (2003–2007), 1490 (2008–2012), and 5437 (2013–present) relevant papers were published in these periods. In Singapore, 50 (1998–2002), 86 (2003–2007), 154 (2008–2012), and 307 (2013–present) relevant papers were published in these periods. During the last 5 years, the number of papers about lymphoma published in Japan increased by 1.5 times compared with the number published between 1998 and 2002, while the numbers of such papers increased by six times during the same period in Korea and Singapore. Surprisingly, the number of such papers published in China increased by 26 times during the last 5 years. Thus, there has been rapid progress in the field of lymphoma research in East Asian countries, although the number of papers published per se might not have any real significance.

We selected the “current status and progress of lymphoma research in East Asian countries” as the main theme and invited four highly respected research groups from East Asian countries, including Japan, to present review articles. I would now like to introduce their four review articles.

From Korea, Dr. Kwai Han Yoo, Dr. Hyewon Lee, and Prof. Cheolwon Suh presented a review article entitled, “Lymphoma epidemiology in Korea and the real clinical field including the Consortium for Improving Survival of Lymphoma (CISL) trial”. Prof. Suh works at the Department of Oncology, Asan Medical Center, University of Ulsan College of Medicine, and is a leader of the CISL of the Korean Society of Hematology Lymphoma Working Party (KSH-LWP). The CISL is an active lymphoma research group and has produced many important papers, especially about NK cell lymphoma and marginal zone lymphoma [7, 8]. Prof. Suh presented a review of Korean lymphoma epidemiology and clinical findings, including those of the CISL trials.

From China, Prof. Yuan-kai Shi, who is a professor of medical oncology at the Department of Medical Oncology, Beijing Key Laboratory of Clinical Study on Anticancer Molecular Targeted Drugs, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, presented a paper entitled, “Current status and progress of lymphoma management in China”. He also developed a novel histone deacetylase inhibitor (HDAC) inhibitor, chidamide (CS055/HBI-8000) [9].

From Singapore, Dr. Jason Yongsheng Chan and Prof. Soon Thye Lim presented a review article entitled, “Novel findings from the Asian Lymphoma Study Group - focus on T and NK-cell lymphomas”. Prof. Lim is a leader of the Asian Lymphoma Study Group, which is active and has produced some important papers, especially about peripheral T-cell lymphoma and NK-cell lymphoma [10]. They introduced many interesting studies about NK-cell lymphoma in their review article.

From Japan, Senior Assist. Prof. Hiroaki Miyoshi and Prof. Koichi Ohshima of the Department of Pathology, Kurume University, presented a review article entitled, “Epidemiology of malignant lymphoma and recent progress of research of adult T-cell leukemia/lymphoma in Japan”. Prof. Ohshima’s group is the most active lymphoma research group in Japan. They have conducted many collaborative studies involving clinical and basic research both inside and outside of Japan. Recently, they produced an important report about programmed cell death ligand 1 (PD-L1) in ATL [11].

We want to experience the passion of the researchers in these countries and share their knowledge.