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Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) accounts for approximately 1% of all lymphomas in our department. In this article, we describe the differential diagnosis of CLL/SLL from other indolent lymphomas, with special reference to follicular lymphoma, marginal zone B-cell lymphoma, lymphoplasmacytic lymphoma, and mantle cell lymphoma, although the latter is considered to be aggressive. CLL/SLL often exhibits proliferation centers, similar to follicular lymphoma. Immunohistological examination can easily distinguish these two lymphomas. The most important characteristic of CLL/SLL is CD5 and CD23 positivity. Mantle cell lymphoma is also CD5-positive and there are some CD23-positive cases. Such cases should be carefully distinguished from CLL/SLL. Some marginal zone lymphomas are also positive for CD5 and such cases are often disseminated. Lymphoplasmacytic lymphoma should also be a differential diagnosis for CLL/SLL. It frequently demonstrates MYD88 L265P, which is a key differential finding. By immunohistological examination, the expression of lymphoid enhancer-binding factor 1 is specific for CLL/SLL and can be a good marker in the differential diagnosis.

Plasma cell type idiopathic multicentric Castleman disease (PC-iMCD) occasionally manifests as parenchymal lung disease. This study aimed to elucidate the detailed clinicopathological features of lung lesions in PC-iMCD and compare the findings with those in immunoglobulin (Ig) G4-related disease (IgG4-RD), the most difficult differential diagnosis of PC-iMCD. We analyzed the clinicopathological findings and immunohistochemical expression patterns of interleukin-6 (IL-6) and Igs in lung specimens from 16 patients with PC-iMCD and 7 patients with IgG4-RD. Histologically, pulmonary PC-iMCD could not be differentiated from IgG4-RD based on lesion distribution patterns, the number of lymphoid follicles and obliterative vasculitis, or fibrosis types. The eosinophil count was higher in the IgG4-RD group than in the PC-iMCD group (p = 0.004). The IgG4/IgG-positive cell ratio was significantly higher in the IgG4-RD group (p < 0.001). The IgA-positive cell count and IL-6 expression intensity were higher in the PC-iMCD group than in the IgG4-RD group (p < 0.001). Based on these findings, we proposed a new diagnostic approach to differentiate lung lesions of PC-iMCD and IgG4-RD. Our approach can be utilized to stratify patients with suspected lung-dominant PC-iMCD to identify candidates for strong immunosuppressive treatment, including IL-6 blockade, at an early stage.

Classic Hodgkin lymphoma (CHL) is a lymphoid neoplasia characterized by the presence of large tumor cells, referred to as Hodgkin and Reed-Sternberg (HRS) cells, originating from B-cells in an inflammatory background. As the clinical significance of B-cell markers has yet to be fully elucidated, this study aimed to clarify the clinicopathological significance of CD79a in 55 patients with CHL. They were immunohistochemically divided into two groups, comprising of 20 CD79a-positive and 35 CD79a-negative patients. There was no significant correlation between CD79a and CD20 expression (rs = 0.125, P = 0.362). CD79a-positive patients were significantly older at onset (P = 0.011). There was no significant correlation between CD79a-positivity and clinical stage (P = 0.203), mediastinal involvement (P = 0.399), extranodal involvement (P = 0.749), or laboratory findings, including serum levels of lactate dehydrogenase (P = 1) and soluble interleukin-2 receptor (P = 0.251). There were significant differences in overall survival (OS) (P = 0.005) and progression-free survival (PFS) (P = 0.007) between CD79a-positive and CD79a-negative patients (5-year OS: 64.6% and 90.5%; 5-year PFS: 44.0% and 76.6%, respectively). Five patients in whom the majority (> 80%) of HRS cells expressed CD79a consisted of 4 males and 1 female aged between 52 and 81 years; 4 of them were in a limited clinical stage. We concluded that CD79a-positive CHL may have unique clinicopathological features.

Plasma cell-type Castleman disease (PCD) is a rare idiopathic atypical lymphoproliferative disorder. It is difficult to differentiate between PCD and IgG4-related disease (IgG4-RD) based on histology alone. As PCD often presents with abundant hemosiderin deposition, lymph node lesions obtained from 22 PCD patients and 12 IgG4-RD patients were analyzed using Prussian blue staining to clarify whether hemosiderin deposition is effective in distinguishing between these two diseases. The analysis disclosed that hemosiderin was more densely deposited in PCD than in IgG4-RD. The median number of Prussian blue-positive cells ± standard deviation (SD) in PCD and IgG4-RD cases was 13 ± 36 cells/3HPFs and 4 ± 8 cells/3HPFs (P = 0.034), respectively. In addition, we analyzed the relationship between hemosiderin deposition and levels of serum interleukin (IL)-6, serum C-reactive protein (CRP), and anemia-related biomarkers. We found that hemosiderin deposition was significantly correlated with the level of serum CRP (P = 0.045); however, no significant correlation was observed between hemosiderin deposition and serum IL-6 levels (P = 0.204). A non-significant positive correlation was observed between hemosiderin deposition and serum hemoglobin levels (P=0.09). Furthermore, no significant correlation was observed between hemosiderin deposition and serum iron levels (P = 0.799). In conclusion, hemosiderin deposition characteristically observed in PCD may be related to the inflammatory aggressiveness of the disease and could be used for its differential diagnosis.

In this paper, we introduce a simplified, one-step procedure for lymphocyte isolation from an endoscopically biopsied fragment. For lymphocyte isolation, an endoscopically harvested specimen and 5 mL of normal saline solution were placed in a wire mesh strainer set in a porcelain bowl. To obtain the lymphocyte suspension, the solid specimen was crushed using the rubber portion of a plunger of a 10 mL injection syringe. Flow cytometry was performed using the lymphocyte suspension. For validating our methods, the one-step lymphocyte isolation technique was used to perform flow cytometry on samples from 23 patients with (n = 12) or without (n = 11) gastrointestinal lymphoma. Flow cytometry of light chain expression was performed in all patient samples (feasibility: 100%). Sensitivity was 83.3% (10/12) and specificity was 100% (11/11). In conclusion, lymphocytes isolated from a single endoscopic biopsy specimen using our simplified and quick procedure are suitable for flow cytometry. Considering that flow cytometry has an important advantage of providing the results on the examination day itself, the results of this study suggest that flow cytometric analysis using our single-step lymphocyte isolation technique can be potentially used to diagnose lymphoma in the gastrointestinal mucosa.