Recently, a unique clinicopathologic variant of multicentric Castleman's disease (MCD) has been identified in Japan. This disease is characterized by a constellation of symptoms, as listed in the title, and multiple lymphadenopathy of mild degree with a pathologic diagnosis of atypical CD, often posing diagnostic and therapeutic problems for pathologists and hematologists, respectively. These findings suggest that this disease represents a novel clinical entity belonging to systemic inflammatory disorders with a background of immunological abnormality beyond the ordinal spectrum of MCD. To define this disorder more clearly, Japanese participants presented clinicopathologic data at the Fukushima and Nagoya meetings. Many of the patients presented by the participants were significantly accompanied by a combination of thrombocytopenia, ascites (anasarca), pleural effusions, microcytic anemia, fever, myelofibrosis, renal dysfunction, and organomegaly (TAFRO). Multiple lymphadenopathies were generally of mild degree, less than 1.5 cm in diameter, and consistently featured the histopathology of mixed- or less hyaline vascular-type CD. Autoantibodies were often detected. However, this disease did not fulfill the diagnostic criteria for well-known autoimmune diseases including systemic lupus erythematosus. Castleman-Kojima disease and TAFRO syndrome (the favored clinical term) were proposed for this disease. The patients were sensitive to steroid and anti-interleukin-6 receptor antibody (tocilizumab), but some exhibited a deteriorated clinical course despite the treatment. The participants proposed a future nationwide survey and a Japanese consortium to facilitate further clinical and therapeutic studies of this novel disease. [J Clin Exp Hematop 53(1): 57-61, 2013]

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and is the most common type of malignant lymphoid neoplasm. While some DLBCLs exhibit strong cell-autonomous survival and proliferation activity, others depend on interactions with non-malignant cells for their survival and proliferation. Recent next-generation sequencing studies have linked these interactions with the molecular classification of DLBCL. For example, germinal center B-cell-like DLBCL tends to show strong associations with follicular T cells and epigenetic regulation of immune recognition molecules, whereas activated B-cell-like DLBCL shows frequent genetic aberrations affecting the class I major histocompatibility complex. Single-cell technologies have also provided detailed information about cell–cell interactions and the cell composition of the microenvironment of DLBCL. Aging-related immunological deterioration, i.e., immunosenescence, also plays an important role in DLBCL pathogenesis, especially in Epstein-Barr virus-positive DLBCL. Moreover, DLBCL in “immune-privileged sites”—where multiple immune-modulating mechanisms exist—shows unique biological features, including frequent down-regulation of immune recognition molecules and an immune-tolerogenic tumor microenvironment. These advances in understanding the immunology of DLBCL may contribute to the development of novel therapies targeting immune systems.

Epstein-Barr virus (EBV) is detected in 20% to 30% of sporadic Burkitt lymphoma (sBL). However, only a few studies of EBV-positive (EBV⁺) sBL have been reported, and its characteristics still remain controversial. To highlight the features of EBV⁺ sBL, we compared the clinicopathologic characteristics of 33 cases of EBV⁺ and 117 cases of EBV-negative (EBV⁻) sBL in Japan. EBV⁺ sBL showed significantly higher age distribution (median, 42 vs. 13 y; P<0.0001) and higher frequency of patients older than 50 years (48% vs. 16%, P<0.0001). We also revealed the difference of the involved sites. The EBV⁺ group showed significantly higher incidence of involvement of tonsil (P=0.027), adrenal gland (P=0.011), and cervical lymph node (P=0.040). In addition, the EBV⁺ group tended to have higher incidence of nodal involvement (P=0.078) and involvement of para-aorta lymph node (P=0.084) and heart (P=0.050). In contrast, the gastrointestinal tract was less frequently affected in EBV⁺ sBL (P=0.024). In addition, the less positivity for MUM1 (P=0.020) of EBV⁺ sBL was highlighted. These results indicate that biological behavior and pathogenesis of EBV⁺ sBL might be different from those of EBV⁻ sBL. Our results demonstrate that EBV⁺ sBL has an aspect of age-related disease and is a distinct clinicopathologic subtype, which should be distinguished from EBV⁻ sBL.

Hodgkin lymphomas (HLs) are lymphoid neoplasms derived from B cells and consist histologically of large neoplastic cells known as Hodgkin and Reed–Sternberg cells and abundant reactive bystander cells. HLs include two main types, classic HL (CHL) and nodular lymphocyte predominant HL (NLPHL). Recent molecular analyses have revealed that an immune evasion mechanism, particularly the PD-1/PD-L1 pathway, plays a key role in the development of CHL. Other highlighted key pathways in CHL are NF-κB and JAK/STAT. These advances have dramatically changed the treatment for CHL, particularly relapsed/refractory CHL. For example, PD-1 inhibitors are now widely used in relapsed/refractory CHL. Compared with CHL, NLPHL is more characterized by preserved B cell features. Overlapping morphological and molecular features between NLPHL and T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) have been reported, and biological continuity between these two entities has been highlighted. Some THRLBCLs are considered to represent progression from NLPHLs. With considerable new understanding becoming available from molecular studies in HLs, therapies and classification of HLs are continually evolving. This paper offers a summary of and update on the pathological and molecular features of HLs for a better understanding of the diseases.