Cutaneous B-cell lymphomas: 2021 update on diagnosis, risk-stratification, and management

Primary Cutaneous B-Cell Lymphoma Co-Existing with Mycosis Fungoides-A Case Report and Overview of the Literature

The existence of two sequential lymphomas, one localized and one systemic, either both with B or T lymphocytes, or one with B cells and one with T cells, with the same patient, is a known possibility. The second lymphoma is often induced by immunodepression or by the initial treatment. However, the existence of two cutaneous lymphomas with different cell lines, without systemic involvement, represents an uncommon situation. In this report, we describe the case of a 37-year-old man with an initial diagnosis of PMZBCL that over 10 months also developed a MF patch/plaque on the left leg.

Update in Diagnosis and Management of Primary Cutaneous B-Cell Lymphomas

Primary cutaneous lymphomas are a rare group of diseases, with an estimated incidence of 0.5-1 case per 100,000 people per year. Primary cutaneous B-cell lymphomas (pCBCLs) represent 25-30% of all primary cutaneous lymphomas. There are three main subtypes of pCBCL: primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma, and primary cutaneous diffuse large B-cell lymphoma, leg type. Cutaneous B-cell lymphomas have a broad spectrum of clinical presentations, which makes diagnostic and therapeutic strategies challenging. To date, treatment recommendations for cutaneous B-cell lymphomas have been largely based on small retrospective studies and institutional experience. Recently, the pharmacotherapeutic landscape has expanded to include drugs that may modify the underlying disease pathology of pCBCLs, representing new therapeutic modalities for this rare group of diseases. Novel therapies used for other systemic B-cell lymphomas show promise for the treatment of pCBCLs and are being increasingly considered. These new therapies are divided into five main groups: monoclonal antibodies, immune checkpoint inhibitors, small-molecule inhibitors, bispecific T-cell engaging, and chimeric antigen receptor T cell. In this review, we discuss the clinical, histopathological, molecular, and cytogenetic features of the most common pCBCL subtypes with a focus on current and innovative therapeutic developments in their management. These emerging treatment strategies for B-cell lymphomas and cutaneous B-cell lymphomas may represent novel first-line options for the management of these rare diseases.

Diffuse Large B-Cell Lymphoma – Rare Presentation

Teaching Point: Subcutaneous nodules sparing the dermis and without extracutaneous involvement is a rare presentation of the diffuse large B-cell lymphoma.

Integrative diagnosis of primary cutaneous large B-cell lymphomas supports the relevance of cell of origin profiling

Primary cutaneous large B-cell lymphomas (PCLBCL) represent a diagnostic challenge because they are classified as PCLBCL, leg type (PCLBCL, LT) or primary cutaneous follicle centre lymphoma, large cell (PCFCL, LC), which differ by prognosis and therapeutic requirement. Unclassified cases with discordant clinical presentations, morphologies, and immunophenotypes may be classified into the not otherwise specified (PCLBCL, NOS) category based on ancillary molecular analyses. Cell-of-origin profiling as germinal centre (GC) type or non-GC type by immunohistochemistry is not considered reproducible because of variable CD10 expression. In a series of 55 PCLBCL cases with > 80% large cells, we reported 21 PCFCL, LC cases as GC-type and 27 PCLBCL, LT as non-GC-type; 7 cases were considered PCLBCL, NOS. Here, we demonstrate the accuracy of molecular profiling of PCLBCL as GC or non-GC type using a reverse transcriptase multiplex ligation assay (RT-MLPA). RT-MLPA classified the seven PCLBCL, NOS cases in accordance with their mutational profile. An integrative principal component analysis confirmed the main criteria and the relevance of genomic profiling of PCFCL, LC as GC-derived, and PCLBCL, LT as non-GC-derived. Both the cell-of-origin classification of PCLBCL and the integrative analysis identified two clinically relevant subgroups according to overall survival, which may help to standardize PCLBCL diagnosis and patient management.

CUTANEOUS B-CELL LYMPHOMAS: UPDATE ON DIAGNOSIS, RISK-STRATIFICATION, AND MANAGEMENT

PCBCLs are a group of Non-Hodgkin's B-cell lymphomas originating in and usually confined to the skin, representing approximately one fourth of primary cutaneous lymphomas (PCL). Their current classification system has been the result of the joint World Health Organization (WHO) - European Organization for Research and Treatment of Cancer (EORTC) consensus in 2018. To date, several types of PCBCLs have been described in the scientific literature, with different clinical presentation and prognosis. Primary cutaneous follicle-center lymphoma (PCFCL) and primary cutaneous marginal zone lymphoma (PCMZL) are the most common forms, with a typical indolent course. On the contrary, primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL, LT) is less common, yet more aggressive, with a reported 5-year overall survival of approximatively 50%. In this review, we outline the PCBCLs defining diagnostic criteria, report the features of the less common subtypes and summarize the noteworthy therapeutical options currently available in this field.

Primary cutaneous follicle center lymphoma with aberrant CD8 expression

We report an unusual case of primary cutaneous follicle center lymphoma (PCFCL) with aberrant expression of the T-cell marker CD8. The patient is a 48-year-old male with no significant past medical history who presented with red indurated plaques on the abdomen. A punch biopsy showed abnormal lymphoid follicles in the dermis with reduced mantle zones and decreased tingible body macrophages. The epidermis was uninvolved. The follicles expressed CD20, PAX-5, and bcl-6 by immunohistochemistry. CD8, however, was strongly positive, highlighting neoplastic cells, which were negative for any additional T-cell markers. TIA and granzyme B were also negative. The patient underwent further staging workup, without evidence of nodal involvement. His course has been indolent thus far. In summary, we present a case of PCFCL with aberrant expression of the T-cell marker CD8, a finding not previously reported in the literature and a potential diagnostic pitfall.