Search

Aims: We applied the 2017 World Health Organization (WHO) classification criteria to categorise a series of 64 primary cutaneous large B-cell lymphomas (PCLBCLs), containing a majority (≥80%) of large cells and a proliferative rate of ≥40%, raising the problem of the differential diagnosis between PCLBCL, leg type (PCLBCL-LT) and primary cutaneous follicle centre lymphoma, large cell (PCFCL-LC). The aims were to determine the reproducibility and prognostic relevance of the 2017 WHO criteria., Methods and Results: Morphology and phenotype identified 32 PCLBCLs-LT and 25 PCFCLs-LC; seven cases (11%) remained unclassified. Morphology was less reproducible than immunophenotype. Pertinent markers for the differential diagnosis were MUM1, FOXP1, CD10, and IgM. bcl-2 and bcl-6 were expressed by both PCFCLs-LC and PCLBCLs-LT at substantial levels. Neither Ki67 expression nor p63 expression was of diagnostic value. MYD88 was found to be mutated only in PCLBCLs-LT (n = 22, 69%). According to Hans/Hans modified algorithms, 23 of 25 PCFCLs-LC had germinal centre (GC) status, and the 32 PCLBCLs-LT had non-GC status. Overall survival was poorer for PCLBCLs-LT than PCFCLs-LC (P = 0.0002). Non-GC cases had poorer overall survival than GC cases (P = 0.0007). In PCLBCLs-LT, MYC expression was associated with cutaneous relapses (P = 0.014). When GC/non-GC status was applied to unclassified cases, only a single case remained discordant., Conclusions: Our results support the 2017 WHO classification criteria for PCLBCL diagnosis. The Hans modified algorithm using CD10 and MUM1 distinguished PCFCLs-LC from PCLBCLs-LT with optimal diagnostic value without requiring bcl-6 immunolabelling (poorly reproducible). Rare unclassified cases may constitute a provisionally heterogeneous subgroup for which GC/non-GC status (relevant for prognosis) may guide therapeutic decisions., (© 2019 John Wiley & Sons Ltd.)

Background: We report the cases of three patients presenting skin lesions whose biopsies showed nodular polymorphic infiltrates consisting of lymphocytes, plasma cells, histiocytes, eosinophils, B blasts, and Hodgkin Reed-Sternberg (HRS)-like cells. Two of them were initially diagnosed as classical Hodgkin lymphoma (cHL), on the other hand, the last one as a B-cell lymphoma. All patients have been treated for angioimmunoblastic T-cell lymphoma (AITL)., Methods: We performed a second review of the skin biopsies with further immunophenotypic molecular analyses. Scrupulous observation revealed, in the background of the three cases, atypical small to medium-sized lymphocytes carrying a CD3+, CD4+ T-cell phenotype and expressing PD1 and CXCL13 follicular helper T-cell markers. The two lesions initially diagnosed as cHL showed scattered HRS-like cells with CD30+, CD15+, PAX5+, CD20-, Epstein Barr Virus (EBV) + classical phenotype. The case initially diagnosed as B-cell lymphoma showed a diffuse B-cell proliferation associated with small B-cell and medium to large-sized B blasts that were positive for EBV., Conclusion: Those cases highlighted that atypical T-cells may be obscured by B-cell proliferation mimicking cHL or B-cell lymphoma in cutaneous localization of AITL and confirmed the requirement of collecting clinical information before performing a diagnosis., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Aims: Distinction between primary cutaneous follicular lymphoma (PCFL) and primary cutaneous marginal zone lymphoma (PCMZL) is challenging, as clear-cut immunophenotypical and cytogenetic criteria to segregate both entities are lacking., Methods and Results: To characterize PCFL and PCMZL more clearly and to define criteria helpful for the differential diagnosis, we compared expression of immunohistochemical markers [LIM-only transcription factor 2 (LMO2), human germinal centre-associated lymphoma (HGAL), stathmin 1 (STMN1), activation-induced cytidine deaminase (AID), myeloid cell nuclear differentiation antigen (MNDA)] and the presence of cytogenetic abnormalities described previously in nodal follicular lymphoma [B cell lymphoma 2 (BCL2) and BCL6 breaks, 1p36 chromosomal region deletion (del 1p36)] in a series of 48 cutaneous follicular and marginal zone lymphomas [cutaneous follicular lymphoma (CFL) and cutaneous marginal zone lymphoma (CMZL)]. Immunostaining for STMN1, LMO2, HGAL and AID allowed the distinction between CFL and CMZL, and STMN1 was the most sensitive marker (100% CFL, 0% CMZL). LMO2, HGAL and AID were positive in 93.2%, 82.1% and 86.2% CFL (all CMZL-negative). MNDA was expressed in both entities without significant difference (10.3% CFL, 30.8% CMZL, P = 0.18). BCL2, BCL6 breaks and the del 1p36 were present in 16.7%, 10.7% and 18.5% CFL and no CMZL. Finally, three and 29 CFL were reclassified as secondary cutaneous follicular lymphomas (SCFL) and PCFL without significant differences concerning phenotypical and cytogenetic features. BCL2, BCL6 breaks and the del 1p36 were present in 11.1%, 8% and 16.7% PCFL and did not impact the prognosis., Conclusion: LMO2, HGAL, STMN1 and AID, but not MNDA, are discriminant for the recognition between CFL and CMZL. BCL2, BCL6 rearrangements and the del 1p36 have a role in the pathogenesis of PCFL, the latest being the most common alteration., (© 2017 John Wiley & Sons Ltd.)