Epstein–Barr virus (EBV)-positive mucocutaneous ulcer (EBVMCU) was first described as a lymphoproliferative disorder in 2010. EBVMCU is a unifocal mucosal or cutaneous ulcer that often occurs after local trauma in patients with immunosuppression; the patients generally have a good prognosis. It is histologically characterized by proliferating EBV-positive atypical B cells accompanied by ulcers. On the basis of conventional pathologic criteria, EBVMCU may be misdiagnosed as EBV-positive diffuse large B-cell lymphoma or other lymphomas. However, its prognosis differs from that of EBV-associated lymphomas, in that patients with EBVMCU frequently show spontaneous regression or complete remission without chemotherapy. Therefore, EBVMCU is now recognized as a low-grade malignancy or a pseudo-malignant lesion. Avoiding unnecessary chemotherapy by distinguishing EBVMCU from other EBV-associated lymphomas will reduce the burden and unnecessary harm on patients. On the basis of these facts, EBVMCU was first described as a new clinicopathological entity by the World Health Organization in 2017. In this review, we discuss the clinicopathological characteristics of previously reported EBVMCU cases, while focusing on up-to-date clinical, pathological, and genetic aspects.

Immunoglobulin G4-related disease (IgG4-RD) is a systemic disorder characterized by tissue fibrosis and intense lymphoplasmacytic infiltration, causing progressive organ dysfunction. Activation-induced cytidine deaminase (AID), a deaminase normally expressed in activated B-cells in germinal centers, edits ribonucleotides to induce somatic hypermutation and class switching of immunoglobulin. While AID expression is strictly controlled under physiological conditions, chronic inflammation has been noted to induce its upregulation to propel oncogenesis. We examined AID expression in IgG4-related ophthalmic disease (IgG4-ROD; n = 16), marginal zone lymphoma with IgG4-positive cells (IgG4+ MZL; n = 11), and marginal zone lymphoma without IgG4-positive cells (IgG4- MZL; n = 12) of ocular adnexa using immunohistochemical staining. Immunohistochemistry revealed significantly higher AID-intensity index in IgG4-ROD and IgG4+ MZL than IgG4- MZL (p < 0.001 and = 0.001, respectively). The present results suggest that IgG4-RD has several specific causes of AID up-regulation in addition to inflammation, and AID may be a driver of oncogenesis in IgG4-ROD to IgG4+ MZL.

Background: Most patients with methotrexate‐associated lymphoproliferative disorder (MTX‐LPD) show diffuse large B‐cell lymphoma (DLBCL) or classic Hodgkin lymphoma (CHL) types. Patients with MTX‐LPD often have spontaneous remission after MTX discontinuation, but chemotherapeutic intervention is frequently required in patients with CHL‐type MTX‐LPD. In this study, we examined whether programmed cell death‐ligand 1 (PD‐L1) expression levels were associated with the prognosis of MTX‐LPD after MTX discontinuation.Methods: A total of 72 Japanese patients diagnosed with MTX‐LPD were clinicopathologically analyzed, and immunohistochemical staining of PD‐L1 was performed in 20 DLBCL‐type and 24 CHL‐type MTX‐LPD cases to compare with the clinical course.Results: PD‐L1 was expressed in 5.0% (1/20) of patients with DLBCL‐type MTX‐LPD, whereas it was expressed in 66.7% (16/24) of the patients with CHL‐type MTX‐LPD in more than 51% of tumor cells. Most CHL‐type MTX‐LPD patients with high PD‐L1 expression required chemotherapy owing to exacerbations or relapses after MTX discontinuation. However, no significant differences in clinicopathologic findings at diagnosis were observed between PD‐L1 high‐ and low‐expression CHL‐type MTX‐LPD.Conclusion: PD‐L1 expression was significantly higher in patients with CHL‐type than DLBCL‐type MTX‐LPD, suggesting the need for chemotherapy in addition to MTX discontinuation in CHL‐type MTX‐LPD patients to achieve complete remission. No association was observed between PD‐L1 expression levels and clinical findings at diagnosis, suggesting that PD‐L1 expression in tumor cells influences the pathogenesis of CHL‐type MTX‐LPD after MTX discontinuation.

Purpose: Many patients with various cancers have received immune checkpoint inhibitors (ICIs) worldwide since their approval, and novel unexpected complications from their long-term use are apparent. We identified some cases of B cell lymphoma occurring during PD-1 blockade therapy as such unexpected complications. In this study, we aimed to evaluate the incidence of hematological malignancies in patients with lung cancer receiving PD-1 blockade therapy and to elucidate the mechanisms underlying the progression of these malignancies. Experimental Design: We performed immunohistochemical staining on the clinical samples from patients with B cell lymphoma that developed during PD-1 blockade therapy and analyzed large-scale real-world datasets. We further investigated the underlying mechanisms through in vitro and in vivo experiments. Results: A higher incidence of B cell malignancies has been observed in patients with lung cancer treated with PD-1 blockade therapies based on large-scale real-world data analyses (n = 15,670). Our identified lymphomas had a large amount of CD4+ T follicular helper (TFH)-cell infiltration. In addition, PD-1 blockade activated PD-1+ TFH cells, which promoted lymphoma proliferation via the IL-4/IL-4R, IL-21/IL-21R, and CD40L/CD40 axes. Notably, the lymphomas exhibited high expression of IL-4R, IL-21R, and CD40. Conclusions: Our findings highlight the need for careful monitoring and consideration of the potential B-cell malignancy complications in clinical settings where ICIs are used.

Gating strategy for T follicular helper (TFH) cells in flow cytometry analysis

Patient selection flowchart in the MDV database