Primary cutaneous large B‐cell lymphomas: relevance of the 2017 World Health Organization classification: clinicopathological and molecular analyses of 64 cases

A Descriptive Study of 103 Primary Cutaneous B-Cell Lymphomas: Clinical and Pathological Characteristics and Treatment from the Spanish Lymphoma Oncology Group (GOTEL)

Primary cutaneous B-cell lymphomas (PCBCLs) are B-cell lymphomas that can occur in the skin without evidence of extracutaneous involvement. The 2005 WHO/EORTC classification of cutaneous lymphomas and its 2018 update have distinguished three main categories based on clinicopathological, immunohistochemical, and genetic characteristics: primary cutaneous marginal zone lymphoma (PCMZL), primary cutaneous follicle centre lymphoma (PCFCL), and primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT). PCMZL and PCFCL are clinically indolent, while PCDLBCL-LT is an aggressive lymphoma. Due to its low incidence and lack of prospective studies, it is difficult to establish a standard treatment for each subgroup. The objective of our study was to describe the clinical and pathological characteristics of 103 patients with cutaneous B-cell lymphoma from 12 centres belonging to the Spanish Lymphoma Oncology Group. The median age was 53 years (40-65). According to skin extension, 62% had single-site lymphoma, 17% had regional lymphoma, and 20% had multifocal lymphoma. Histology: 66% had PCMZL, 26% had PCFCL, and 8% had PCDLBCL-LT. Twenty-three percent of the patients were treated exclusively with surgery, 26% with radiotherapy only, 21% with surgery plus radiotherapy, 10% with polychemotherapy, and 5% with rituximab monotherapy. Overall, 96% of patients achieved a complete response, and 44% subsequently relapsed, most of them relapsing either locally or regionally. The 10-year OS was 94.5% for the entire cohort, 98% for the PCMZL cohort, 95% for the PCFCL cohort, and 85.7% for the PCDLBCL-LT cohort. Our data are comparable to those of other published series, except for the high frequency of PCMZL. The expected heterogeneity in therapeutic management has been observed.

Clinico-Pathological, Cytogenetic and Molecular Profiles of Primary Cutaneous Diffuse Large B-Cell Lymphomas

We analyzed the clinico-pathological, cytogenetic and molecular features of 18 Primary Cutaneous Diffuse Large B-Cell Lymphoma (PCDLBCL), and 15 DLBCL secondarily localized to the skin (SCDLBCL), highlighting biologic similarities and differences between the two groups. PCDLBCL were sub classified after histopathological review as PCDLBCL-Leg type (PCDLBCL-LT, 10 cases) and the PCDLBCL-not otherwise specified (PCDLBCL, NOS, 8 cases). Immunohistochemistry for Hans' algorithm markers, BCL2, and MYC was performed. The molecular study included the determination of the cell of origin (COO) by Lymph2Cx assay on Nano string platform, FISH analysis of IgH, BCL2, BCL6, and MYC genes, as well as the mutation analysis of MYD88 gene. At immunohistochemistry, BCL2 and MYC hyper expression was more frequent in LT than in NOS cases and, according to Hans' algorithm, PCDLBCL LT were mostly of the non-GC type (8/10), whereas in PCDLBCL NOS the GC type prevailed (6/8). The determination of COO using Lymph2Cx supported and further confirmed these results. At FISH analysis, all but one LT cases versus 5 out of 8 PCDLBCL NOS showed at least one gene rearrangement among IgH, BCL2, MYC or BCL6. In addition, MYD88 mutations were more frequently present in LT than in NOS subtypes. Interestingly, MYD88- mutated patients were older, with a non-GC phenotype and had worse OS, compared to MYD88 WT cases. Overall, SCDLBCL did not show, at the genetic and expression level, different profiles than PCDLBCL, even if they bear a significantly worse prognosis. At survival analysis, the most important prognostic factors in PCDLBCL patients were age and MYD88 mutation, whereas relapse and high Ki67 expression were relevant in SCDLBCL patients. Our study comprehensively analyzed the clinico-pathological and molecular features of PCDLBCL LT, PCDLBCL-NOS, and SCDLBCL, underlining the differnces among them and the importance of properly identifying these entities at the time of diagnosis.

Disease-Defining Molecular Features of Primary Cutaneous B-Cell Lymphomas: Implications for Classification and Treatment

Primary cutaneous B-cell lymphoma-primary cutaneous follicle center lymphoma; primary cutaneous marginal zone lymphoma; and primary cutaneous diffuse large B-cell, leg type-is a heterogeneous group with a variety of clinical and histological presentations. Until recently, the molecular bases of these disease subtypes have been unclear. We and others have identified the specific genetic characteristics that distinguish these subtypes from their respective systemic counterparts. These molecular features can improve diagnoses, determine the likelihood of concurrent or future systemic disease, and enable the rational design of novel clinical trials.

Proliferative Tumor-Infiltrating Lymphocytes' Abundance within the Microenvironment Impacts Clinical Outcome in Cutaneous B-Cell Lymphomas

Primary cutaneous large B-cell lymphoma, leg-type (PCLBCL-LT) is the most aggressive primary cutaneous B-cell lymphoma (PCBCL). Tumor microenvironment has a crucial role in tumor development, and tumor-infiltrating lymphocytes (TILs) can be targeted by immunotherapies. We characterized TILs in 20 PCBCLs to identify the tumor microenvironment features associated with clinical outcomes. We developed a seven‒multiplex immunofluorescence panel using Opal staining and image analysis using HALO software. In PCLBCL-LT, TILs were sparsely intermingled within tumor infiltrate in contrast to those in indolent PCBCL where TILs were scattered around tumor nodule edges with variable tumor infiltration. In PCLBCL-LT, TILs were composed of CD8 and CD4, whereas CD4 was predominant in indolent PCBCL. Proliferative TILs (CD3+Ki-67+ cells) were more abundant in PCLBCL-LT (P = 0.0036) than in indolent PCBCL. In PCLBCL-LT, proliferative TILs' abundance tended to be associated with better progression-free survival. These data were confirmed in a second independent cohort of 23 cases showing that proliferative TILs were more abundant in PCLBCL-LT (P = 0.0205) and that in PCLBCL-LT, high CD3+Ki-67+ cell density was associated with better progression-free survival (P = 0.002). These distinct TILs composition and distribution among PCBCL suggest that proliferative T lymphocytes represent a good prognostic factor in PCLBCL-LT and that stimulating their functions may represent a therapeutic approach.

Panel Sequencing of Primary Cutaneous B-Cell Lymphoma

Background: Primary cutaneous follicular B-cell lymphoma (PCFBCL) represents an indolent subtype of Non-Hodgkin’s lymphomas, being clinically characterized by slowly growing tumors of the skin and common cutaneous relapses, while only exhibiting a low propensity for systemic dissemination or fatal outcome. Up to now, only few studies have investigated underlying molecular alterations of PCFBCL with respect to somatic mutations. Objectives: Our aim was to gain deeper insight into the pathogenesis of PCFBCL and to delineate discriminatory molecular features of this lymphoma subtype. Methods: We performed hybridization-based panel sequencing of 40 lymphoma-associated genes of 10 cases of well-characterized PCFBCL. In addition, we included two further ambiguous cases of atypical B-cell-rich lymphoid infiltrate/B-cell lymphoma of the skin for which definite subtype attribution had not been possible by routine investigations. Results: In 10 out of 12 analyzed cases, we identified genetic alterations within 15 of the selected 40 target genes. The most frequently detected alterations in PCFBCL affected the TNFRSF14, CREBBP, STAT6 and TP53 genes. Our analysis unrevealed novel mutations of the BCL2 gene in PCFBCL. All patients exhibited an indolent clinical course. Both the included arbitrary cases of atypical B-cell-rich cutaneous infiltrates showed somatic mutations within the FAS gene. As these mutations have previously been designated as subtype-specific recurrent alterations in primary cutaneous marginal zone lymphoma (PCMZL), we finally favored the diagnosis of PCMZL in these two cases based on these molecular findings. Conclusions: To conclude, our molecular data support that PCFBCL shows distinct somatic mutations which may aid to differentiate PCFBCL from pseudo-lymphoma as well as from other indolent and aggressive cutaneous B-cell lymphomas. While the detected genetic alterations of PCFBCL did not turn out to harbor any prognostic value in our cohort, our molecular data may add adjunctive discriminatory features for diagnostic purposes on a molecular level.

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.

Characterization of Primary and Secondary Cutaneous B-Cell Lymphomas: A Population-Based Study of 4758 Patients

INTRODUCTION/BACKGROUND

Cutaneous B-cell lymphomas are a heterogeneous group of rare malignancies whose specific site tropisms and site-specific survival have not been well documented. In this study, we seek to investigate the frequency and survival for primary and secondary cutaneous MZL (pcMZL and scMZL), primary and secondary cutaneous FCL (pcFCL and scFCL), and primary and secondary cutaneous DLBCL (pcDLBCL and scDLBCL) to better understanding their prognosis and natural history.

MATERIALS AND METHODS

A total of 4758 cases of CBCL diagnosed between 1975 and 2016 were identified in the SEER-18 database. Statistical analysis was performed to identify the frequency of location and survival.

RESULTS

pcMZL was disproportionately likely to present on the face and upper limb while those of scMZL approximated the expected ratios based on body surface area. pcFCL and scFCL were more likely to present on the face and scalp/neck. pcDLBCL and scDLBCL were more likely to present on the face, scalp/neck, and lower limb. Patients with systemic MZL or FCL, but not DLBCL, had significantly better survival than those diagnosed in the skin than at other sites.

CONCLUSIONS

All of these lymphomas demonstrate site-specific tropisms and survival. Molecular characterization of cutaneous lymphomas with analyses of tumor microenvironment are the next steps in understanding disease biology.

Cell-of-origin classification using the Hans and Lymph2Cx algorithms in primary cutaneous large B-cell lymphomas

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) and primary cutaneous follicle center lymphoma with a diffuse population of large cells (PCFCL-LC) are both primary cutaneous B-cell lymphomas with large-cell morphology (CLBCL) but with different clinical characteristics and behavior. In systemic diffuse large B-cell lymphoma, not otherwise specified (DLBCL-NOS), gene-expression profiling (GEP) revealed two molecular subgroups based on their cell-of-origin (COO) with prognostic significance: the germinal center B-cell-like (GCB) subtype and the activated B-cell-like (ABC) subtype. This study investigated whether COO classification is a useful tool for classification of CLBCL. For this retrospective study, 51 patients with PCDLBCL-LT and 15 patients with PCFCL-LC were analyzed for their COO according to the immunohistochemistry-based Hans algorithm and the NanoString GEP-based Lymph2Cx algorithm. In PCFCL-LC, all cases (100%) classified as GCB by both Hans and Lymph2Cx. In contrast, COO classification in PCDLBCL-LT was heterogeneous. Using Hans, 75% of the PCDLBCL-LT patients classified as non-GCB and 25% as GCB, while Lymph2Cx classified only 18% as ABC, 43% as unclassified/intermediate, and 39% as GCB. These COO subgroups did not differ in the expression of BCL2 and IgM, mutations in MYD88 and/or CD79B, loss of CDKN2A, or survival. In conclusion, PCFCL-LC uniformly classified as GCB, while PCDLBCL-LT classified along the COO spectrum of DLBCL-NOS using the Hans and Lymph2Cx algorithms. In contrast to DLBCL-NOS, the clinical relevance of COO classification in CLBCL using these algorithms has limitations and cannot be used as an alternative for the current multiparameter approach in differentiation of PCDLBCL-LT and PCFCL-LC.

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.

[Impact of algorithms proposed by the Cutaneous Lymphoma French Study Group for diagnosis of cutaneous lymphoproliferations]

After a first diagnosis proposition, management of cutaneous lymphomas requires a systematic review by an expert pathologist and each case is presented to a multidisciplinary meeting in the setting of the French Study Group of Cutaneous Lymphomas to propose an adequate treatment. A retrospective study of the 2760 cutaneous lymphoproliferations retrieved between 2010 and 2011 were analyzed and demonstrated the interest of diagnostic algorithms we built with the group. The objective of our study was to compare two cohorts from 2010-2011 and 2015-2017 regarding the proportion of cases sent for validation or expertise, the concordance and mismatch rates and potential diagnostic issues using our diagnostic algorithms. Between 2015-2017, 5640 skin lymphoproliferation cases were examined. It appeared that Pathologists were more confident and effective in finding the right diagnosis. Indeed, the rate of concordant diagnosis increased from 57% to 67%. Moreover, in comparison with the 2010-2011 concordant cases sent for expertise, 73.5% of concordant cases were sent for validation in 2015-2017. 14% of cases remained discordant, mainly sent for expertise. Furthermore, half of questionable cases (26.3%) were resolved after expertise, and 12.1% cases remained unsolved. These priority cases are important to be presented at multidisciplinary meeting. The analysis of discordant and doubtful cases unveiled recurrent diagnostic problems for which we proposed appropriate diagnostic algorithms including large B cell lymphomas, CD4+ T cell lymphoproliferations, epidermotropic CD8+ T-cell lymphoproliferations and the differential diagnosis of mycosis fongoïdes/Sezary syndrome versus inflammatory dermatitis.

Double expressor and double/triple hit status among primary cutaneous diffuse large B-cell lymphoma: a comparison between leg type and not otherwise specified subtypes

Primary cutaneous diffuse large B-cell lymphomas (pcDLBCLs) are rare hematological neoplasms. The pcDLBCL category includes primary cutaneous large B-cell lymphoma leg type (pcDLBCL-LT), characterized by a particularly unfavorable outcome, and primary cutaneous large B-cell lymphoma not otherwise specified (pcDLBCL-NOS), a widely debated subentity with a more indolent course. The negative prognostic impact of double expressor status (DE status, given by coexpression of MYC and BCL2) and double hit/triple hit status (DH/TH status, given by translocations of MYC and BCL2 and/or BCL6) in nodal DLBCL is well known; however, no unanimous conclusions regarding relevance of DE and DH/TH status have been reached in pcDLBCL. Therefore, our purpose has been to investigate the presence and prognostic relevance of DE and DH/TH status among a retrospective multicentric cohort of 16 cases of pcDLBCL-LT and 17 cases of pcDLBCL-NOS. All cases were thoroughly reevaluated, both on a morphological and immunohistochemical level, and tested by means of fluorescence in situ hybridization for MYC, BCL2 and BCL6 rearrangements. DE status was observed in 69% of pcDLBCL-LT cases and in 24% of pcDLBCL-NOS cases; however, it did not impact prognosis in any of the groups examined. Combining molecular results, we highlighted a relevant fraction of DH pcDLBCL cases (three pcDLBCL-LT cases and one pcDLBCL-NOS case) and the very first case of TH pcDLBCL-LT reported to date. All DH cases were characterized by MYC and BCL6 rearrangements. Overall, DH/TH cases represented 15% (5/33) of all pcDLBCLs and were mostly pcDLBCL-LT. DH/TH status and DH status alone were associated with poorer overall survival and disease-specific survival (both p < 0.05) among all pcDLBCLs, without reaching statistical significance in the pcDLBCL-LT and pcDLBCL-NOS groups. In conclusion, MYC, BCL2, and BCL6 cytogenetical testing could be useful in identifying a putative subset of more aggressive pcDLBCLs, although this observation has to be confirmed by further studies.

Epidemiological changes in cutaneous lymphomas: an analysis of 8593 patients from the French Cutaneous Lymphoma Registry

BACKGROUND

Primary cutaneous lymphomas (PCLs) are a heterogeneous group of T-cell (CTCL) and B-cell (CBCL) malignancies. Little is known about their epidemiology at initial presentation in Europe and about potential changes over time.

OBJECTIVES

The aim of this retrospective study was to analyse the frequency of PCLs in the French Cutaneous Lymphoma Registry (GFELC) and to describe the demography of patients.

METHODS

Patients with a centrally validated diagnosis of primary PCL, diagnosed between 2005 and 2019, were included.

RESULTS

The calculated incidence was unprecedently high at 1·06 per 100 000 person-years. The number of included patients increased yearly. Most PCL subtypes were more frequent in male patients, diagnosed at a median age of 60 years. The relative frequency of rare CTCL remained stable, the proportion of classical mycosis fungoides (MF) decreased, and the frequency of its variants (e.g. folliculotropic MF) increased. Similar patterns were observed for CBCL; for example, the proportion of marginal-zone CBCL increased over time.

CONCLUSIONS

Changes in PCL frequencies may be explained by the emergence of new diagnostic criteria and better description of the entities in the most recent PCL classification. Moreover, we propose that an algorithm should be developed to confirm the diagnosis of PCL by central validation of the cases.

Cutaneous Lymphomas -Part II: Other Cutaneous Lymphomas

Primary cutaneous T-cell lymphomas other than mycosis fungoides, Sézary syndrome, and lymphoproliferative CD30⁺ disorders are few, accounting for less than 5% of all cutaneous lymphomas. A cytotoxic phenotype is characteristic of these tumors, and their clinical behavior is usually aggressive. Patients often present with extracutaneous symptoms or develop them shortly after diagnosis. Management is usually multidisciplinary, and intensive systemic therapy and bone marrow transplantation should be considered. Cutaneous B-cell lymphomas account for approximately 30% of primary cutaneous lymphomas. They make up a heterogeneous group of tumors that have different clinical and pathological features. Clinical course also varies. Presenting as papules, nodules, or tumors of variable reddish-violaceous coloring, the lesions may be solitary or multiple and occasionally form clusters. There may also be generalized lesions, present at multiple sites on the trunk, head, or extremities. Three well-defined groups of primary cutaneous lymphoma have been reported: follicle center lymphoma; marginal zone lymphoma, which follows an indolent course; and a diffuse large B-cell lymphoma, leg type, which follows an aggressive course.

Secondary cutaneous involvement by direct extension in high-grade B-cell lymphomas

Cutaneous involvement by a systemic lymphoma via direct extension is a very rare phenomenon, historically described in patients who had advanced-stage disease with bulky lymphadenopathy. Since its original description, most cases of cutaneous lymphomatous spread via direct extension are attributable to Hodgkin disease. Here, we report the occurrence of direct cutaneous dissemination in the setting of nodal high-grade B-cell lymphomas, specifically diffuse large B-cell lymphoma (DLBCL) and B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and classical Hodgkin lymphoma (also called gray-zone lymphoma). Both cases are adequately documented with clinical, histopathologic, and immunophenotypic data, as well as additional cytogenetic analysis.

Primary Cutaneous B-Cell Lymphomas: An Update

Primary cutaneous B-cell lymphomas (PCBCLs) comprise a group of extranodal B-cell non-Hodgkin lymphomas B-cell derived, which primarily involve the skin without evidence of extracutaneous disease at the time of diagnosis. They include ~25% of all cutaneous lymphomas and are classified in three major subgroups (World Health Organization (WHO) 2017): primary cutaneous marginal zone lymphoma (PCMZL), primary cutaneous follicle-center cell lymphoma (PCFCL), and diffuse large B-cell lymphoma, leg type (PCDLBCL, LT). This classification also includes some less common entities such as intravascular large B-cell lymphoma. Recently, WHO-EORTC added Epstein-Barr virus positive (EBV+) mucocutaneous ulcer, as a new provisional distinct entity, to cutaneous B-cell lymphomas. PCBCLs are classically characterized by patches, plaques, or nodules showing great variability for color, shape, and location. Diagnosis requires histological examination with immunohistochemical staining. In general, therapeutic options depend on the exact histological and immunohistochemical classification, disease presentation, and risk assessment. PCMZL and PCFCL are considered indolent lymphomas with a good prognosis and are associated with 5-year disease-specific survival ≥ 95%. In contrast, PCDLBCL, LT is considered an aggressive lymphoma with a survival rate in 5 years of lower than 60%. Patients with a solitary lesion or limited lesions in a single anatomical site require different treatments as compared to patients with generalized lesions or refractory disease or extracutaneous involvement. Therapeutic choice includes observation, local, or systemic therapy based on histology and disease extension. Patient management is multidisciplinary, including dermatologists, pathologists, hemato-oncologists, and radiation oncologists.

MYD88 in the driver's seat of B-cell lymphomagenesis: from molecular mechanisms to clinical implications

More than 50 subtypes of B-cell non-Hodgkin lymphoma (B-NHL) are recognized in the most recent World Health Organization classification of 2016. The current treatment paradigm, however, is largely based on 'one-size-fits-all' immune-chemotherapy. Unfortunately, this therapeutic strategy is inadequate for a significant number of patients. As such, there is an indisputable need for novel, preferably targeted, therapies based on a biologically driven classification and risk stratification. Sequencing studies identified mutations in the MYD88 gene as an important oncogenic driver in B-cell lymphomas. MYD88 mutations constitutively activate NF-κB and its associated signaling pathways, thereby promoting B-cell proliferation and survival. High frequencies of the hotspot MYD88(L265P) mutation are observed in extranodal diffuse large B-cell lymphoma and Waldenström macroglobulinemia, thereby demonstrating this mutation's potential as a disease marker. In addition, the presence of mutant MYD88 predicts survival outcome in B-NHL subtypes and it provides a therapeutic target. Early clinical trials targeting MYD88 have shown encouraging results in relapsed/refractory B-NHL. Patients with these disorders can benefit from analysis for the MYD88 hotspot mutation in liquid biopsies, as a minimally invasive method to demonstrate treatment response or resistance. Given these clear clinical implications and the crucial role of MYD88 in lymphomagenesis, we expect that analysis of this gene will increasingly be used in routine clinical practice, not only as a diagnostic classifier, but also as a prognostic and therapeutic biomarker directing precision medicine. This review focuses on the pivotal mechanistic role of mutated MYD88 and its clinical implications in B-NHL.

Large B - Cell Lymphoma of the Leg - Unfavourable Course with Rituximab/Bendamustin

BACKGROUND:

Cutaneous B-cell lymphomas represent about 25% of all cutaneous lymphomas. Peripheral diffuse large B-cell lymphoma of the leg type is the most aggressive subtype seen mainly in elderly patients. Treatment is not standardised.

CASE REPORT:

An 87-year-old female patient was presented in May 2018 because of the development of painless subcutaneous nodules on the legs since late 2017. On examination, we observed up to 5 cm large erythematous nodules on the legs and a smaller plaque in the left submammary fold. The histology of a skin demonstrated tumour infiltrate that was separated from the overlying epidermis by a grenz zone. It consisted of densely packed, blastoid lymphocytic cells with numerous, and some atypical mitoses. The cells were positive for CD20, CD79A and CD5. Almost 100% of the cells were labelled with Ki67. The diagnosis of a diffuse large B-cell lymphoma (PCLBCL-LT) of the leg was confirmed. Histologic analysis of a bone marrow biopsy demonstrated a hypercellular bone marrow without malignant lymphatic infiltrates. Diagnostic ultrasound of cervical nodes and computerised tomography (CT) scans (native and with contrast medium) of head, neck and trunk excluded an extracutaneous manifestation of the PCLBCL-LT. Treatment with rituximab plus bendamustibe was initiated, but tumour progress was noted after the second course. Suggested palliative therapy with radiation and rituximab was refused. The patient died 7 months after diagnosis.

CONCLUSIONS:

Although some trials suggested a beneficial effect of immuno-chemotherapy, the prognosis of (PCLBCL-LT) remains poor. Standardised treatment is missing due to the relative rarity of this malignancy.

Mutations of the B-Cell Receptor Pathway Confer Chemoresistance in Primary Cutaneous Diffuse Large B-Cell Lymphoma Leg Type

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCLBCL-LT) preferentially involves the lower limb in elderly subjects. A combination of polychemotherapy and rituximab has improved prognosis. However, about 50% of patients will experience progression or relapse without any predictive biologic marker of therapeutic response. The mutational profile of PCLBCL-LT has highlighted mutations contributing to constitutive NF-κB and B-cell receptor (BCR) signaling pathways but has not demonstrated clinical utility. Therefore, the mutational status of 32 patients with PCLBCL-LT (14 patients with complete durable response and 18 patients with relapsing or refractory disease) was determined with a dedicated lymphopanel. Tumor pairs at diagnosis and relapse or progression were analyzed in 14 relapsing or refractory patients. Patients with PCLBCL-LT harboring one mutation that targets one of the BCR signaling genes, CD79A/B or CARD11, displayed a reduced progression-free survival and specific survival (median 18 months, P = 0.002 and 51 months, P = 0.03, respectively, whereas median duration in the wild-type group was not reached) and were associated with therapeutic resistance (P = 0.0006). Longitudinal analyses revealed that MYD88 and CD79B were the earliest and among the most mutated genes. Our data suggest that evaluating BCR mutations in patients with PCLBCL-LT may help to predict first-line therapeutic response and to select targeted therapies.