Classic Hodgkin lymphoma (CHL) was first described in 1832 by Thomas Hodgkin, and is characterized by a small number of Hodgkin and Reed–Sternberg cells in a rich inflammatory background. However, even in this modern era, due to the histological and biological overlap with CHL and other B-cell malignancies, including mediastinal grey zone lymphoma and other lymphomas accompanied by “Hodgkinoid cells”, their discrimination is challenging and sometimes impossible. The complexity and ambiguity of the boundaries of CHL and its related diseases make the definition of CHL unresolved. Our group has studied the significance of PD-L1 expression and infection of Epstein-Barr virus (EBV) in the diagnosis of CHL, emphasizing their pathological role, clinical significance, and high reproducibility even in daily clinical practice. In this review, we summarize the diagnostic strategy of CHL and its histological lookalikes based on neoplastic PD-L1 expression and infection of EBV, and attempt a reappraisal of the definition of CHL.

Follicular lymphoma (FL) is an indolent B-cell lymphoma with a germinal center (GC) B cell phenotype that typically harbors t(14;18)(q32;q21). t(14;18) juxtaposes IGH on 14q32 and BCL2 on 18q21, resulting in overexpression of the anti-apoptotic BCL2 protein. However, t(14;18) is also found in the peripheral blood or lymphoid nodes (LNs) of otherwise healthy individuals. Moreover, overt FL has several additional gene alterations involved in epigenetic modification, JAK/STAT signaling, immune modulation, and NF-κB signaling, indicating multi-step lymphomagenesis in FL. There are two early or precursory lesions of FL: t(14;18)-positive cells in the peripheral blood of otherwise healthy individuals and in situ follicular B-cell neoplasm (ISFN). t(14;18)-positive cells are found in 10%–50% of healthy populations, and their incidence and frequency increase with age. The detection of t(14;18) in peripheral blood is a predictive factor for an increased risk of overt FL development. In contrast, ISFN is a histopathologically recognizable precursory lesion, in which t(14;18)-positive cells are confined to the GC of otherwise reactive LNs. ISFN is usually detected incidentally, with an incidence ranging from 2.0% to 3.2%. Occasional ISFN cases have concurrent or metachronous clonally related overt FL or aggressive B-cell lymphoma of a GC phenotype. t(14;18)-positive cells in peripheral blood and isolated ISFN, by themselves, are asymptomatic with limited clinical significance; however, investigations of t(14;18)-positive precursory or early lesions offer meaningful insights into the pathogenesis of FL. This review summarizes the epidemiology, clinical features, pathology, and genetics of precursory or early lesions of FL.

Recently, the ratio of C-reactive protein to albumin (CAR) is used as an inflammatory marker that has been demonstrated to be a simple and reliable prognostic factor in solid tumors and hematological malignancy. However, no studies of the CAR have been performed in patients with adult T-cell leukemia-lymphoma (ATL). We retrospectively analyzed the clinical features and outcomes in 68 newly diagnosed acute- and lymphoma-type ATL [(acute-(n=42) or lymphoma-type (n=26)] patients in Miyazaki Prefecture from 2013 to 2017. Furthermore, we investigated correlations between pretreatment CAR levels and clinical features. The median age was 67 years (range, 44 - 87). Patients were initially treated by either palliative therapy (n=14) or chemotherapy [n=54; CHOP therapy (n=37)/ VCAP-AMP-VECP therapy (n=17)], and showed median survival durations of 0.5 months and 7.4 months, respectively. The factors affecting OS by multivariate analysis were age, BUN, and CAR. Importantly, we revealed that the high CAR group (optimal cut-off point; 0.553) was a significant indicator of worse OS by multivariate analysis (p< 0.001, HR; 5.46). The median survival of patients with a CAR< 0.553 was 8.37 months, while patients with a CAR>0.553 had a median survival of 3.94 months. The different clinical features between high CAR and low CAR groups were hypoproteinemia and the implementation of chemotherapy. Furthermore, in the chemotherapy group, but not the palliative therapy group, CAR was a significant prognostic marker. Our study indicated that CAR may be a new simple and significant independent prognostic marker in acute- and lymphoma-type ATL patients.

We conducted this study with the objective of elucidating the mechanism of development of fibrosis in hematologic neoplasms and develop treatments for these patients. Among the suggested mechanisms of development of fibrosis is cases of hematologic neoplasms is the production of TGF-beta1 (transforming growth factor-beta-1) and TNF-alpha1 (tumor necrotizing factor-alpha-1) by the tumor cells, both of which are fibrosis-stimulating cytokines that act on fibroblasts to promote fibrosis. However, there are few reports based on human clinical pathology studies. We conducted an immunohistochemical study on paraffin-embedded formalin-fixed specimens obtained from 104 patients with various pathologic conditions (acute leukemia, malignant lymphoma, inflammation, cancer, etc.). The association of tissue fibrosis with positive immunohistochemistry for TGF- beta1 and/or TNF-alpha1, TGF-beta1 was found to be strongly associated with tissue fibrosis, and in cases with positive immunohistochemistry for TGF-beta1, the odds ratio for fibrosis was 12.8, which was significantly high. Combined positivity for TGF-beta1 and TNF-alpha1 was also associated with a significant odds ratio for fibrosis of 3.4, suggesting that TGF-beta1 expression is an important prerequisite. TGF-beta1 has been suggested as playing a relatively important role in tissue fibrosis. Future clinical application of these cytokines for both diagnosis and treatment is expected.

Epstein-Barr virus-positive mucocutaneous ulcer (EBVMCU) is a newly recognized disease entity characterized by EBV-positive atypical B-cell proliferation. EBVMCU is a localized self-limited disease that affects mucosa and skin, especially the oral cavity. EBVMCU develops in immunosuppressive patients, such as those with methotrexate (MTX)-administrated rheumatoid arthritis (RA). Here we clinicopathologically analyzed 12 EBVMCU patients in a single institution. All cases were administrated MTX for RA, and five cases occurred in the oral cavity. All cases except one had demonstrated spontaneous regression after withdrawal of the immunosuppressive agent. We found 4 of 5 cases in the oral cavity had preceding traumatic events in the same site within a week before the onset of EBVMCU. Although there is no detailed and large study that has analyzed the trigger of EBVMCU, a traumatic event would indeed be a significant trigger for EBVMCU in the oral cavity. The cases were histologically classified; six cases were diffuse large B-cell lymphoma-type, five were polymorphous-type, and one was Hodgkin-like lesion type due to morphological appearance and immunophenotype. The PD-L1 expression was also examined by two antibodies for PD-L1 (E1J2J and SP142). Both antibodies revealed identical results for PD-L1 expression, and three cases were positive for PD-L1. The application of SP142 for evaluating the immune status of lymphomagenesis has also been proposed. Nine of 12 cases were negative for PD-L1, which implies that most EBVMCU cases may be caused by an immunodeficiency, rather than an immune-evasion, mechanism. However, as three cases were positive for PD-L1, immune escape may underly the pathogenesis in a subset of EBVMCU cases.

We retrospectively evaluated long-term outcomes of high dose chemotherapy followed by autologous stem cell transplant (HDC/ASCT) in patients with diffuse large B-cell lymphoma (DLBCL). Between 2004 and 2020, 46 DLBCL patients received HDC/ASCT in our institution, including 12 patients (26.1%), who received as an upfront setting (UFS). At a median follow-up time of 69 months (range, 2-169 months), the 5-year progression-free survival (PFS) rates were 82.5% (95%CI, 46.1-95.3%) in the UFS, and 57.8% (95%CI, 38.1-73.2%) in the relapsed or refractory (R/R) patients (n=34), respectively. The 5-year PFS rates were 62.3% (95%CI, 34.0-81.3%) in primary resistant (n=13) or early relapsing (within 1 year from the initial diagnosis) patients (n=4), and 53.3% (95%CI, 25.9-74.6%) in those relapsing >1 year after the initial diagnosis (n=17), with no statistically significant difference (p=0.498). In R/R patients, multivariate analysis showed that the remission status before HDC/ASCT was an independent poor prognostic factor for progression-free survival (hazard ratio [HR], 17.0; 95%CI, 3.35-86.6; p=0.000630) and high-risk category in the international prognostic index for OS (HR, 9.39; 95%CI, 1.71-51.6; p=0.0100). The incidence of non-relapse mortality by 5 years, and 10 years were 12.2%, and 15.2%, respectively. Eleven patients (23.9%) developed second malignancies, which was the most frequent late complication after HDC/ASCT, with 5-year, and 10-year cumulative incidence of 16.9%, 22.5%, respectively. In conclusion, HDC/ASCT is effective for chemo-sensitive R/R DLBCL regardless of the timing and lines of therapy. However, careful observation is required, considering the long-term complications such as secondary malignancies.

A Japanese subgroup analysis from the Asian phase II study of darinaparsin in patients with relapsed or refractory peripheral T-cell lymphoma (PTCL) was performed to evaluate the efficacy and safety outcomes of the Japanese population. In this Asian phase II study, darinaparsin was administered to 65 patients, including 37 Japanese patients. In the Japanese population, the histopathological type of PTCL was PTCL, not otherwise specified in 26 patients (70.3%), angioimmunoblastic T-cell lymphoma in 9 patients (24.3%) and anaplastic large cell lymphoma, anaplastic lymphoma kinase (ALK) -negative in 2 patients (5.4%), and the median patient age was 70.0 (range: 43-85). 94.6% and 35.1% of the Japanese population had previously received multi-agent and single-agent regimen, respectively. The efficacy and safety were summarized and compared between the overall and Japanese populations. Based on central assessment, the overall response rate was 22.2% (8/36; 90% confidence interval [CI]: 11.6-36.5) in the Japanese population and 19.3% (11/57; 90% CI: 11.2-29.9) in the overall population. There were no essential differences in the safety profile of darinaparsin between the Japanese population and the overall population. The results of this subgroup analysis indicate that the efficacy and safety profiles of the Japanese subpopulation were broadly consistent with that of the overall population, and that darinaparsin is potentially an effective treatment with a manageable safety profile in Japanese patients with relapse or refractory PTCL.

High-grade B-cell lymphoma with 11q aberrations (HGBL-11q) has been classified for the first time as a high-grade mature B-cell neoplasm according to the 5th edition of the World Health Organization Classification of Tumors of Hematopoietic and Lymphoid Tissues. HGBL-11q is morphologically and immunohistochemically similar to Burkitt lymphoma (BL) or HGBL; it is characterized by gain in the 11q23.2-11q23.3 region and loss in the 11q24.1-qter region but it lacks MYC translocation. HGBL-11q is a rare tumor, and its exact frequency in Japan remains unclear. In this study, we classified 113 Germinal center B-cell (GCB) type aggressive B-cell lymphomas (BCLs), which were divided into BL, high-grade (HG), and large cell (LC) morphologies. We performed fluorescence in situ hybridization (FISH) to identify 11q aberrations. Nine patients had 11q aberrations (7.96%, 9/113), including six HGBL-11q. The age range was from 8 to 87 years, and all were male. Six out of 14 patients with HG morphology were diagnosed with HGBL-11q (6/14, 42.9%). HGBL-11q has been found to occur primarily in children and young adults but also in middle-aged and older adults. Patients with HG morphology without MYC translocation should undergo FISH for 11q aberrations regardless of age. However, the pathogenesis, clinical findings, and prognosis of HGBL-11q remain unclear. The accumulation of cases with an accurate HGBL-11q diagnosis in daily practice and accurate and detailed data on HGBL-11q will contribute to further understanding of 11q aberrations.

Small lymphocytic lymphoma (SLL) is a rare disease subtype which has the same morphological and immunophenotypic features as chronic lymphocytic leukemia (CLL) but does not demonstrate lymphocytosis and grows mainly in the lymph nodes and spleen. As with CLL, SLL patients tend to present with immune abnormalities, and are associated with an increased risk for developing second primary malignancies. We report here two cases of SLL who developed lung cancer concurrently. The biological and clinical features of these two patients were very similar to each other; they both developed SLL with trisomy 12 and lacked lymphocytosis or cytopenia. SLL cells involved nodal areas adjacent to lung adenocarcinoma which expressed PD-L1. One patient received immunochemotherapy including nivolumab and ipilimumab against lung cancer, and notably, transient deterioration of SLL occurred after the second cycle of immunochemotherapy along with the development of immune related adverse events. Immunohistochemical analysis of the SLL samples of the patient revealed that the tumor cells were positive for CTLA-4, suggesting that ipilimumab might have potentially induced the activation of SLL cells by blocking the inhibitory signal mediated by CTLA-4. These clinical findings indicate the potential biological relationship between SLL and lung cancer. According to these observations, we would like to draw attention to the possibility of deterioration of SLL when immune checkpoint inhibitors are used for the treatment of malignancies developed in SLL patients.

Myeloid sarcoma (MS) is a condition characterized by a tumor mass of myeloid blasts in any site of the body other than the bone marrow, with or without acute myeloid leukemia. A 93-year-old man underwent laparoscopy-assisted distal gastrectomy with D1 lymphadenectomy for advanced gastric cancer. Other than metastatic foci of gastric cancer cells, some dissected lymph nodes showed destructive architecture with proliferation of small- to medium-sized atypical hematopoietic cells. Those cells were focally positive for naphthol AS-D chloroacetate esterase. Immunohistochemically, positive results were obtained for CD4, CD33, CD68 (KP1), Iba-1, lysozyme, myeloperoxidase, and PU.1, with focally positive results for CD13, CD14, CD68 (PGM1), CD163, and CD204, and negative results for AE1/AE3, CD1a, CD3, CD20, and S-100 protein. These results suggested MS with phenotypically myelomonocytic differentiation. We report a rare case of MS incidentally found in specimens resected for other purposes. Careful diagnosis and consideration of differential diagnoses including MS using an adequate panel of antibody markers for dissected lymph nodes is warranted.