Cutaneous lymphomas

The fifth edition of the WHO-Classification - what is new for cutaneous lymphomas?

The recently published 5th edition of the "World Health Organization classification of hematolymphoid tumors: lymphoid neoplasms" provides a hierarchical reorganization. In general, new (definitive) entities as well as tumor-like lesions were included. Primary cutaneous B-cell lymphomas (CBCL) received a thorough review. A new class/family of cutaneous follicle center lymphomas was defined. Primary cutaneous marginal zone lymphoma is now presented as a separate entity independent from extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. In primary cutaneous T-cell lymphoma, former provisional entities were upgraded to definite entities. Sézary Syndrome was sorted into the class/family of mature T-cell and NK-cell leukemias. Additionally, a newly formed entity of primary cutaneous peripheral T-cell lymphoma, NOS was created for CTCL entities that do not fit into the already described CTCL entities. The increasing importance of genomic and molecular data has already been recognized in classifying leukemias and systemic lymphomas. However, in PCL the genomic landscape has not yet been fully described and validated. Therefore, future research is necessary to describe the genomic and molecular mechanisms underlying the disease entities more clearly. This would both meet a diagnostic need and valuably contribute to future classification schemes.

Primary cutaneous diffuse large B-cell lymphoma, NOS and leg type: Clinical, morphologic and prognostic differences

BACKGROUND AND OBJECTIVES

Primary cutaneous diffuse large B-cell lymphoma, NOS (PCLBCL/NOS) is a rare PCLBCL. Only few data are available for this tumor. The aim of this study was to identify clinical and/or immunohistochemical markers (in addition to Bcl-2) that characterize PCLBCL/NOS, assist in differentiating it from PCLBCL, leg type (PCLBCL/LT) and help to assess the clinical course/prognosis.

PATIENTS AND METHODS

Bcl-2^- PCLBCL/NOS) cases (n = 14 were compared with Bcl-2⁺ PCLBCL/LT cases (n = 29).

RESULTS

PCLBCL/NOS patients were younger, predominantly male and had better survival rates than patients with PCLBCL/LT. Patients with PCLBCL/NOS presented more often with larger plaques limited to one or two contiguous body regions, whereas PCLBCL/LT cases often presented with disseminated lesions. Neoplastic cells had a higher proliferation rate (Ki67) in PCLBCL/LT patients. The tumor microenvironment of PCLBCL/NOS had a more prominent CD3⁺ infiltrate. Overall survival data for the whole cohort (n = 37) revealed that female gender and Bcl-2 expression correlated with a worse survival rate. Bcl-6 expression and centroblastic subtype correlated with better outcomes. None of the other markers studied (e.g. GCB/non-GCB subtype) correlated with survival rate.

CONCLUSIONS

PCLBCL/NOS and PCLBCL/LT differ in their clinical behavior and outcomes. Bcl-2 still seems to be the best marker for discriminating between these two subgroups. Bcl-2, female gender and Bcl-6 represent prognostic markers for PCLBCL.

Silencing autocrine death: a ubiquitin ligase that blocks activation-induced cell death in cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) tumor cells lack the ability of activated T cells to undergo TCR/CD3-mediated activation-induced cell death (AICD). In this issue, the study reported by Wu et al. demonstrates that c-CBL (Casitas B-lineage Lymphoma proto-oncogene) is overexpressed in CTCL. When CTCL cells lose c-CBL, AICD is enhanced. Furthermore, combination therapy with methotrexate (a known demethylating agent for the CD95 gene) in combination with the loss of c-CBL increases CTCL cell death. Therefore, inhibition of c-CBL could represent a method of sensitizing lymphoma cells to enhance AICD. Armed with their novel data, the investigators envision combination therapies that target c-CBL to reactivate AICD in the malignant T cells whenever responsiveness to TCR/CD3 signaling is retained.