Primary cutaneous peripheral T-cell lymphoma, not otherwise specified: results of a multicentre European Organization for Research and Treatment of Cancer (EORTC) cutaneous lymphoma taskforce study on the clinico-pathological and prognostic features

BACKGROUND

Cutaneous peripheral T-cell lymphoma, not otherwise specified (PTL NOS) is an aggressive, but poorly characterized neoplasm.

OBJECTIVES

The European Organization for Research and Treatment of Cancer cutaneous lymphoma taskforce (EORTC CLTF) investigated 33 biopsies of 30 patients with primary cutaneous PTL NOS to analyse their clinical, histological, immunophenotypic features and outcome.

METHODS

Retrospective analysis of clinical data and histopathological features by an expert panel.

RESULTS

Cutaneous PTL NOS manifested clinically either with solitary or disseminated rapidly grown ulcerated tumours or disseminated papulo-nodular lesions. Histologically, a mostly diffuse or nodular infiltrate in the dermis and often extending into the subcutis was found. Epidermotropism was rarely present and only mild and focal. Unusual phenotypes were frequent, e.g. CD3⁺ /CD4^- /CD8^- and CD3⁺ /CD4⁺ /CD8⁺ . Moreover, 18% of the cases exhibited an aberrant expression of the B-cell marker CD20 by the tumour cells. All solitary tumours were located on the limbs and presented a high expression of GATA-3 but this did not correlate with outcome and therefore could not serve as a prognostic factor. The prognosis was shown to be generally poor with 10 of 30 patients (33%) dying of lymphoma within the follow-up of 36 months (mean value; range 3-144). The survival rates were 61% after 3 years (CI, 43-85%) and 54% after 5 years (CI, 36-81%). Small to medium-sized morphology of tumour cells was associated with a better outcome than medium to large or large tumour cells. Age, gender, clinical stage, CD4/CD8 phenotype and GATA-3 expression were not associated with prognosis. Chemotherapy was the most common treatment modality, but surgical excision and/or radiotherapy may represent an appropriate first-line treatment for solitary lesions.

CONCLUSIONS

Cutaneous PTL NOS shows an aggressive course in most patients independent of initial presentation, age and phenotype. Cytomorphology was identified as a prognostic factor. The data indicate a need for more effective treatment modalities in PTL NOS.

Neoadjuvant immunotherapy with combined ipilimumab and nivolumab in patients with melanoma with primary or in transit disease

The introduction of new therapeutic agents has revolutionized the treatment of metastatic melanoma. The approval of adjuvant anti-programmed death-1 monotherapy with nivolumab or pembrolizumab, and dabrafenib plus trametinib has recently set a new landmark in the treatment of stage III melanoma. Now, clinical trials have shown that immune checkpoint blockade can be performed in a neoadjuvant setting, an approach established as a standard therapeutic approach for other tumour entities such as breast cancer. Recent studies suggest that a pathological response achieved by neoadjuvant immunotherapy is associated with long-term tumour control and that short neoadjuvant application of checkpoint inhibitors may be superior to adjuvant therapy. Most recently, neoadjuvant ipilimumab plus nivolumab in stage III melanoma was reported. With two courses of dose-optimized ipilimumab (1 mg kg^-1 ) combined with nivolumab (3 mg kg^-1 ), pathological responses were observed in 77% of patients, while only 20% of patients experienced grade 3 or 4 adverse events. However, the neoadjuvant trials employing combined immune checkpoint blockade conducted so far have excluded patients with in transit metastases, a common finding in stage III melanoma. Here we report four patients with in transit metastases or an advanced primary tumour who have been treated with neoadjuvant ipilimumab plus nivolumab according to the OpACIN-neo trial scheme (arm B). All patients achieved radiological disease control and a pathological response. None of the patients has relapsed so far. Linked Comment: Blankenstein and van Akkooi. Br J Dermatol 2020; 183:421-422.

The PROCLIPI international registry of early-stage mycosis fungoides identifies substantial diagnostic delay in most patients

BACKGROUND

Survival in mycosis fungoides (MF) is varied and may be poor. The PROCLIPI (PROspective Cutaneous Lymphoma International Prognostic Index) study is a web-based data collection system for early-stage MF with legal data-sharing agreements permitting international collaboration in a rare cancer with complex pathology. Clinicopathological data must be 100% complete and in-built intelligence in the database system ensures accurate staging.

OBJECTIVES

To develop a prognostic index for MF.

METHODS

Predefined datasets for clinical, haematological, radiological, immunohistochemical, genotypic, treatment and quality of life are collected at first diagnosis of MF and annually to test against survival. Biobanked tissue samples are recorded within a Federated Biobank for translational studies.

RESULTS

In total, 430 patients were enrolled from 29 centres in 15 countries spanning five continents. Altogether, 348 were confirmed as having early-stage MF at central review. The majority had classical MF (81·6%) with a CD4 phenotype (88·2%). Folliculotropic MF was diagnosed in 17·8%. Most presented with stage I (IA: 49·4%; IB: 42·8%), but 7·8% presented with enlarged lymph nodes (stage IIA). A diagnostic delay between first symptom development and initial diagnosis was frequent [85·6%; median delay 36 months (interquartile range 12-90)]. This highlights the difficulties in accurate diagnosis, which includes lack of a singular diagnostic test for MF.

CONCLUSIONS

This confirmed early-stage MF cohort is being followed-up to identify prognostic factors, which may allow better management and improve survival by identifying patients at risk of disease progression. This study design is a useful model for collaboration in other rare diseases, especially where pathological diagnosis can be complex.

Cooperation of BRAF(F595L) and mutant HRAS in histiocytic sarcoma provides new insights into oncogenic BRAF signaling

Activating BRAF mutations, in particular V600E/K, drive many cancers and are considered mutually exclusive with mutant RAS, whereas inactivating BRAF mutations in the D(594)F(595)G(596) motif cooperate with RAS via paradoxical MEK/ERK activation. Due to the increasing use of comprehensive tumor genomic profiling, many non-V600 BRAF mutations are being detected whose functional consequences and therapeutic actionability are often unknown. We investigated an atypical BRAF mutation, F595L, which was identified along with mutant HRAS in histiocytic sarcoma and also occurs in epithelial cancers, melanoma and neuroblastoma, and determined its interaction with mutant RAS. Unlike other DFG motif mutants, BRAF(F595L) is a gain-of-function variant with intermediate activity that does not act paradoxically, but nevertheless cooperates with mutant RAS to promote oncogenic signaling, which is efficiently blocked by pan-RAF and MEK inhibitors. Mutation data from patients and cell lines show that BRAF(F595L), as well as other intermediate-activity BRAF mutations, frequently coincide with mutant RAS in various cancers. These data define a distinct class of activating BRAF mutations, extend the spectrum of patients with systemic histiocytoses and other malignancies who are candidates for therapeutic blockade of the RAF-MEK-ERK pathway and underscore the value of comprehensive genomic testing for uncovering the vulnerabilities of individual tumors.

CD68 expression is a discriminative feature of indolent cutaneous CD8-positive lymphoid proliferation and distinguishes this lymphoma subtype from other CD8-positive cutaneous lymphomas

BACKGROUND

Indolent cutaneous CD8+ lymphoid proliferation is a recently described rare entity among cutaneous T-cell lymphomas that typically presents with solitary skin lesions at acral sites. Separation from otherwise aggressive T-cell lymphomas bearing a cytotoxic CD8+ phenotype is fundamental to avoid unnecessary harmful treatment. However, up to now, no reliable discriminative marker has been identified.

OBJECTIVES

Motivated by these diagnostic quandaries, we have analyzed a large series of archived formalin-fixed paraffin-embedded (FFPE) specimens of atypical CD8+ cutaneous infiltrates with clear-cut diagnosis and clinical follow-up (n = 44) including five cases of indolent CD8+ lymphoid proliferation by using immunohistochemistry with the aim of obtaining markers predictive of subtype assignment.

RESULTS

We identified exclusive expression of CD68 by lymphoma cells within the subgroup of indolent CD8+ lymphoid proliferation (5/5 cases). Specific CD68 expression in this entity was confirmed by the application of several monoclonal antibodies (KP1, PG-M1, KiM1P) against the CD68 molecule available for FFPE tissue. In contrast, none of the infiltrates of the other CD8+ cutaneous lymphoma entities stained positive for CD68 (0/39).

CONCLUSIONS

Based on these observations, we suggest CD68 as a new discriminative marker which is helpful in distinguishing indolent CD8+ lymphoid proliferation from other CD8+ cutaneous lymphomas in ambiguous cases.

[Infectious lymphadenitis]

Infectious lymphadenitis is often biopsied in the differential diagnoses of malignant disease. Since the repertoire of lymph nodes which react to exogenous stimuli is limited, malignant lymphomas may enter the clinical and morphological differential diagnosis. In a morphological sense, infectious lymphadenitis is defined as an infection of lymph node tissue. Therefore, the effector phase of the inflammatory reaction will act against lymphatic tissue, in contrast to common physiological hyperplasia. Follicular reactions, in addition to follicular hyperplasia, are seen in HIV-associated lymphadenopathy. Other viruses, such as infectious mononucleosis, give rise to a cytotoxic T-cell reaction. Most infections, however, induce a histiocytic reaction; depending on the microorganism, this varies morphologically from a small clustered epithelioid cell reaction or histiocytic abscesses to epithelioid necrotizing granulomata.

[Lymphomas of the spleen]

The spleen is commonly affected by malignant lymphomas and the macroscopic findings of the spleen correlate with different lymphoma entities. However, most lymphomas are not primarily diagnosed in splenectomy specimens. Exceptions include splenic marginal zone lymphomas and hepatosplenic T-cell lymphomas that are typically diagnosed from histological findings. In addition, hairy-cell leukemia, LGL leukemia and T-cell prolymphocytic leukemia typically show characteristic patterns of infiltration in the spleen which may be diagnostically useful. The different infiltration patterns of these tumors are discussed here.

Periphere NK/T-Zell-Lymphome

Peripheral T-cell lymphomas comprise 8% of the malignant lymphomas in Germany. About 25% of these cases present primarily in extranodal localizations. Such localizations are typical for the respective disease and form the basis for the classification of extranodal peripheral T-cell lymphoma. The morphology, immunophenotype and lineage specificity of the tumor cells (originating from T- or NK-cells) is only secondary for the classification. Extranodal NK/T-cell lymphomas of the nasal type are characterized by an angiocentric growth pattern and large confluent areas of necrosis. In addition, there is a clonal infection by Epstein-Barr virus in the T-lymphocytes. In the differential diagnosis, B-cell lymphomas are more frequent at all localizations than T- or NK-cell lymphomas.

[Cutaneous B-cell lymphoma. Classification and diagnostics]

Primary cutaneous B-cell lymphomas include cutaneous follicle centre lymphoma (PCFCL), cutaneous marginal zone B-cell lymphoma (PCMZL) and cutaneous diffuse large B-cell lymphoma (PCLBCL) "leg type" which are the three main types in the new WHO-EORTC classification for cutaneous lymphomas. PCFCL and PCMZL are indolent lymphomas with an excellent prognosis while PCLBCL shows an aggressive clinical course. All three types must be distinguished from a secondary skin involvement by systemic lymphomas. Since histological and immunohistochemical findings are not decisive, making this distinction requires appropriate staging procedures. In contrast, the pathologist can make an important contribution to the differential diagnosis between neoplastic and reactive cutaneous lymphoproliferations.

Nodal peripheral T-cell lymphomas correspond to distinct mature T-cell populations

Peripheral T-cell lymphomas (PTCL) have not been successfully correlated with specific developmental stages of reactive T-cells. Mature T-cells pass through distinct stages upon antigen encounter. Naïve T-cells are CD45RA(+)/CD45R0(-)/CD27(+)/CCR7(+). After antigen contact they replace CD45RA expression with CD45R0. The mature T-cells differentiate to central memory cells, which retain CD27 and CCR7, or to effector memory cells, which lose expression of both molecules depending on the strength of the antigen interaction. In this study, we evaluated lymph node biopsies from eight PTCL-not otherwise specified (PTCL-NOS), seven angioimmunoblastic T-cell lymphomas (AILT), and 15 anaplastic large cell lymphomas (ALCL). Detection of tumour cells with antibodies that recognize specific rearranged T-cell receptor Vbeta segments allowed us to investigate the expression of various differentiation-associated molecules. Results were analysed by hierarchical cluster analysis. All AILT and ALCL showed a homogeneous effector cell phenotype (CD45RA(-)/CD45R0(+)/CD27(-)), but differed in the cytotoxic and activation markers expressed. Several (5/8) PTCL-NOS clustered together; these cases all exhibited a CD4(+) central memory cell phenotype (CD45RA(-)/CD45R0(+)/CD27(+)) and four expressed the lymph node homing receptor CCR7. In conclusion, AILT and ALCL tumour cells correspond to different subsets of effector cells, while a subset of PTCL-NOS correlates with a non-effector T-cell population.

Extrafollicular proliferation of B cells in the absence of follicular hyperplasia: a distinct reaction pattern in lymph nodes correlated with primary or recall type responses

AIMS

Extrafollicular activation of B cells is rarely observed in human lymph nodes. The aim of this study was to extensively analyse the expression of surface molecules and transcription factors in four such cases, comparing them with follicular B cells and medullary cord plasma cells.

METHODS AND RESULTS

Various combinations of B-cell-related surface markers and transcription factors were studied by triple immunofluorescence. While in the germinal centre, reactive immunoglobulin production occurred exclusively in non-proliferating cells, in extrafollicular activation proliferation of B cells and immunoglobulin production coexisted. In two of these cases proliferating cells were mainly IgG+CD27+, i.e. derived from class-switched postgerminal centre memory B cells. Some of these cells expressed CD30. In the other two cases, immunoglobulin-forming cells were non-class-switched IgM+CD27- B cells, representing a primary expansion of naive B cells.

CONCLUSIONS

Extrafollicular B-cell activation is the morphological correlate of rapid B-cell responses that do not involve the germinal centres. It is pathogenetically heterogeneous, comprising primary responses that occur prior to, or independent of, germinal centre reaction or memory cell activation in recall responses.

[Anaplastic large cell lymphomas lack the expression of T-cell receptor molecules]

Anaplastic large cell lymphoma (ALCL) designates a heterogeneous group of CD30+ (systemic or primary cutaneous) peripheral T-cell lymphomas (PTCLs). A subgroup of systemic ALCL is transformed by anaplastic lymphoma kinase (ALK). We compared 46 ALCL with 22 PTCLs in terms of T-cell receptor (TCR) rearrangements, expression of TCRs and TCR-associated molecules [CD3, ZAP-70 (zeta-associated protein 70)]. Despite their frequent clonal rearrangement for TCRbeta, only 4% of ALCLs expressed TCRbeta protein, whereas TCRs were detected in 86% of PTCLs. Moreover, both TCRbeta+ ALCLs lacked CD3 and ZAP-70 (ie, molecules indispensable for the transduction of cognate TCR signals). Defective expression of TCRs is a common characteristic of all types of ALCL, which may contribute to the dysregulation of intracellular signaling pathways controlling T-cell activation and survival. This molecular hallmark of ALCL is analogous to defective immunoglobulin expression distinguishing Hodgkin lymphoma from other B-cell lymphomas.

Signalling by the oncogenic receptor tyrosine kinase Xmrk leads to activation of STAT5 in Xiphophorus melanoma

Overexpression of the mutationally activated Xmrk receptor initiates the formation of hereditary malignant melanoma in the fish Xiphophorus. In addition to transcriptional overexpression a cell-type specific signal transduction is essential for Xmrk mediated tumor formation. To elucidate the consequence of Xmrk signalling and to identify target proteins that characterize the tumor phenotype, we analysed proteins that are strongly tyrosine phosphorylated in the fish melanoma cell line PSM. One of the most prominent phosphotyrosine proteins was found to be the signal transducer and activator of transcription STAT5. In a heterologous cell system (murine pro B-cells), activation of the Xmrk kinase in a chimeric receptor induced tyrosine phosphorylation, nuclear translocation and DNA binding of STAT5. Following receptor stimulation, expression of the STAT5 specific target genes cis, osm and pim-1 was induced. In Xiphophorus PSM cells STAT5 was found to be preferentially localized in the nucleus, but treatment with tyrphostin AG555, a specific Xmrk kinase-inhibitor, blocked nuclear localization. In these cells as well as in Xiphophorus melanoma expression of pim-1 and constitutive DNA-binding activity of STAT5 was detectable. This constitutive activity was higher in malignant than in benign melanomas, indicating that STAT5 activation is correlated with the malignancy of these tumors.