Artificial intelligence in digital pathology of cutaneous lymphomas: A review of the current state and future perspectives.

Primary cutaneous lymphomas (CLs) represent a heterogeneous group of T-cell lymphomas and B-cell lymphomas that present in the skin without evidence of extracutaneous involvement at time of diagnosis. CLs are largely distinct from their systemic counterparts in clinical presentation, histopathology, and biological behavior and, therefore, require different therapeutic management. Additional diagnostic burden is added by the fact that several benign inflammatory dermatoses mimic CL subtypes, requiring clinicopathological correlation for definitive diagnosis. Due to the heterogeneity and rarity of CL, adjunct diagnostic tools are welcomed, especially by pathologists without expertise in this field or with limited access to a centralized specialist panel. The transition into digital pathology workflows enables artificial intelligence (AI)-based analysis of patients' whole-slide pathology images (WSIs). AI can be used to automate manual processes in histopathology but, more importantly, can be applied to complex diagnostic tasks, especially suitable for rare disease like CL. To date, AI-based applications for CL have been minimally explored in literature. However, in other skin cancers and systemic lymphomas, disciplines that are recognized here as the building blocks for CLs, several studies demonstrated promising results using AI for disease diagnosis and subclassification, cancer detection, specimen triaging, and outcome prediction. Additionally, AI allows discovery of novel biomarkers or may help to quantify established biomarkers. This review summarizes and blends applications of AI in pathology of skin cancer and lymphoma and proposes how these findings can be applied to diagnostics of CL.

Profiling of Copy Number Alterations Using Low-Coverage Whole-Genome Sequencing Informs Differential Diagnosis and Prognosis in Primary Cutaneous Follicle Center Lymphoma.

Primary cutaneous follicle center lymphoma (PCFCL) has an excellent prognosis using local treatment, whereas nodal follicular lymphoma (nFL), occasionally presenting with cutaneous spread, often requires systemic therapy. Distinction of the 2 diseases based on histopathology alone might be challenging. Copy number alterations (CNAs) have scarcely been explored on a genome-wide scale in PCFCL; however, they might serve as potential biomarkers during differential diagnosis and risk stratification. Low-coverage whole-genome sequencing is a robust, high-throughput method for genome-wide copy number profiling. In this study, we analyzed 28 PCFCL samples from 20 patients and compared the copy number profiles with a cohort of diagnostic samples of 64 nFL patients. Although the copy number profile of PCFCL was similar to that of nFL, PCFCL lacked amplifications of 18q, with the frequency peaking at 18q21.33 in nFL cases involving the BCL2 locus (PCFCL: 5.0% vs nFL: 31.3%, P = .018, Fisher exact test). Development of distant cutaneous spread was significantly associated with higher genomic instability including the proportion of genome altered (0.02 vs 0.13, P = .033) and number of CNAs (2 vs 9 P = .017), as well as the enrichment of 2p22.2-p15 amplification involving REL and XPO1 (6.3% vs 60.0%, P = .005), 3q23-q24 amplification (0.0% vs 50.0%, P = .004), 6q16.1-q23.3 deletion (6.3% vs 50.0%, P = .018), and 9p21.3 deletion covering CDKN2A and CDKN2B loci (0.0% vs 40.0%, P = .014, all Fisher exact test) in PCFCL. Analysis of sequential tumor samples in 2 cases harboring an unfavorable clinical course pointed to the acquisition of 2p amplification in the earliest common progenitor underlining its pivotal role in malignant transformation. By performing genome-wide copy number profiling on the largest patient cohort to date, we identified distinctive CNA alterations conceivably facilitating the differential diagnosis of PCFCL and secondary cutaneous involvement of nFL and potentially aiding the risk stratification of patients with PCFCL in the future.

Urticarial mycosis fungoides: A distinctive presentation with blood involvement and a peculiar immunophenotype.

Mycosis fungoides (MF) has been widely reported to mimick a considerable number of different dermatoses, including scarring alopecia, bullous dermatoses or cysts, and comedones. In atypical presentations, histopathology is essential for the diagnosis. We present two cases of MF with clinical urticarial lesions and a striking blood involvement that responded to mogamulizumab treatment. Histopathologically, both cases had classic MF features and shared a peculiar immunophenotype, with positivity for CD25 and FOXP3. Differential diagnoses included urticarial lymphomatoid drug reactions and other lymphomas, like T-cell prolymphocytic leukemia, atypical Sézary syndrome, or adult T-cell lymphocytic leukemia. A low suspicion threshold is necessary for the diagnosis of atypical presentations of MF.

Synchronous occurrence of primary cutaneous B-cell lymphoma and cutaneous Rosai-Dorfman disease in distinct lesions: A unique association.

Rosai-Dorfman disease, also known as sinus histiocytosis with massive lymphadenopathy (SHML), is a rare subtype of reactive histiocytosis which is seldom associated with Hodgkin's and non-Hodgkin's lymphomas. To date, the coexistence in the same patient of extra nodal SHML and primary cutaneous B-cell lymphoma (PCBCL) has been reported in the literature, as metachronous diagnosis in the anatomical area of the original PCBCL or synchronous occurrence in the same lesions. However, no data have been published as for synchronous occurrence of the two pathological entities in distinct anatomical sites. Herein, we report the first ever described synchronous occurrence of PCBCL and SHML, detected in distinct lesions, affecting the same patient. The complete resolution of the patient's PCBCL after rituximab treatment and the concomitant regression of SHML suggest that this clinically benign reactive histiocytic proliferation, potentially triggered by the lymphoma microenvironment itself, may take place not only in the site of the PCBCL lesion, but also in other distant areas not directly affected by the primary cutaneous lymphoma.

Psychological Distress and Treatment Outcome in Patients With Early-Stage Mycosis Fungoides.

BACKGROUND: Skin diseases have been shown to worsen psychological distress, which, in turn, may be detrimental to treatment outcomes. Both the impact of psychological distress on response to treatment in mycosis fungoides (MF) and the effect of treatments on psychological well-being are unclear. OBJECTIVES: To evaluate (1) the association between pretreatment psychological morbidity and treatment outcome in early-stage MF and (2) the impact of response to treatment on psychological well-being. METHODS: This was a prospective cohort study of patients with early-stage MF who started a new stage-directed treatment for their disease. The response was determined using the modified severity-weighted assessment tool, and psychological distress was assessed using the 12-item General Health Questionnaire (GHQ-12) and Penn State Worry Questionnaire (PSWQ). Participants were followed for 1 year. RESULTS: In all, 24 consecutive patients were recruited. Objective response rate was 71% (17/24), consistent with existing literature. Prior to treatment, 9 patients (38%) had clinically significant psychological distress on the GHQ-12, while 8 (33%) demonstrated high-level worry on the PSWQ. Of these patients, 6 had pathologic scores on both instruments. Patients with significantly less baseline anxiety/depression on the GHQ-12 responded better to treatment than patients with higher levels (P = .004). In addition, responders' mean GHQ-12 scores decreased by 39% and their PSWQ scores by 17%, whereas nonresponders' GHQ-12 scores increased by 93% (P = .042) and their PSWQ scores by 11% (P = .019). CONCLUSIONS: These findings suggest that (1) baseline psychological distress is associated with worse outcomes in patients with early-stage MF and that (2) effective treatment improves psychological morbidity.

The evolving role of reduced-dose total skin electron beam therapy in skin malignancies: the renaissance of a rare indication.

Definitive radiation therapy is an effective local treatment for several cutaneous malignancies. Patients with diffuse or generalized skin manifestations might require total skin electron beam therapy (TSEBT) as an alternative treatment to the chasing technique. In this short communication, we highlight the evolving role of TSEBT and present its role in various forms of skin malignancies.

What Is New in Cutaneous T Cell Lymphoma?

PURPOSE OF REVIEW: This review focuses on updates in prognosis, pathogenesis, and treatment of cutaneous T cell lymphoma (CTCL). RECENT FINDINGS: Cohort studies indicate imaging may be necessary in early-stage CTCL. Risk factors for progression of CTCL have been identified. Interactions between malignant cells and the tumor microenvironment (TME) and the skin microbiome advance the understanding of pathogenesis and tumor cell dissemination. Studies support a hypothesis of circulating malignant tumor cells. MicroRNA (miR) influence tumor progression and prognosis; the IL22-STAT3-CCL20 cascade may be a novel target. IL-4, IL-5, and IL-31 cytokines are relevant for pruritus and could be targets for therapeutic interventions. Systemic therapies, such as JAK inhibitors, targeted antibodies, and checkpoint inhibitors, show promise in advanced stages. Allogenic hematopoietic stem cell transplantation provides a potential curative option for patients. Further investigations of prognosis and translational research are necessary to improve stratification of patients for treatment.

Clinical Features, Histological Characteristics, and Disease Outcomes of Mycosis Fungoides in Children and Adolescents: A Nationwide Multicentre Cohort of 46 Patients.

BACKGROUND: Our objective was to describe the clinical, histological characteristics, and disease outcome of a cohort of mycosis fungoides (MF) diagnosed during childhood including disease status at adulthood. METHODS: This is a retrospective multicentre survey of patients aged under 18 years at diagnosis with histologically confirmed MF. Patients' clinical and histological characteristics, treatments, and disease outcome (for patients followed for more than 12 months) were analysed. RESULTS: Forty-six patients were included (median age at diagnosis: 11 years; M:F sex ratio: 3:1) with 39 (85%) followed for at least 12 months. Thirty-nine patients (85%) had stage I MF. Hypopigmented patches were observed in 48% and folliculotropism in 43% patients. Immunophenotype of the skin infiltrate was predominantly CD8+ in 17% of patients. Initial management included a wait-and-see strategy in 6/39 (15%), skin-directed treatment in 27 (69%), and systemic treatment in 6 (15%) patients, respectively, with partial or complete clinical response (PR or CR) observed in 28 patients (72%). 14/39 patients (36%) relapsed after initial response. After a median follow-up period of 54 months, disease status at last news was PR or CR in 31/39 (79%), stable disease in 6 (15%), and progression in 2 (5%) patients. Histological transformation was observed in 3/39 (8%). Of the 15 patients followed until adulthood, 13 (87%) had persistent MF. DISCUSSION: This survey confirms the high frequency of hypopigmented and folliculotropic lesions and of CD8+ immunophenotype compared to adult MF patients. The long-term course is usually indolent but transformation may occur sometimes long after disease onset and the disease may persist during adulthood.

Pediatric Primary Cutaneous Lymphoma in China: A Retrospective Study.

BACKGROUND: The incidence and clinical features of primary cutaneous lymphoma (PCL) tend to differ by age, gender, geographical, and racial variation. All-aged and adult groups of PCL in various regions have been well demonstrated and compared, while the research concentrating on pediatric PCL is rare, especially in Asian countries. OBJECTIVE: The aim of this study was to investigate the clinical characteristics of PCL in pediatric population at a single center in China. METHODS: We conducted a retrospective study of 101 pediatric cases with PCL, diagnosed at the Institute of Dermatology, Chinese Academy of Medical Sciences, from January 2010 to December 2021. RESULTS: Mycosis fungoides (MF), accounting for 41.6% of the total cases, was the most common subtype in pediatric PCL, and the hypopigmented MF accounted for 47.6% of all the MF cases. Lymphomatoid papulosis and chronic active Epstein-Barr virus infection tied for second place with a proportion of 22.8%. Primary cutaneous anaplastic large cell lymphoma, subcutaneous panniculitis-like T-cell lymphoma, primary cutaneous peripheral T-cell lymphoma, rare subtypes and primary cutaneous B-cell lymphoma, respectively, accounted for 2.0%, 4.0%, 4.0%, and 3.0%. Most patients had favorable prognosis during the follow-up. CONCLUSION: The study suggested that MF was the most common subtype in pediatric PCL in China, and most types of pediatric PCL had favorable prognosis.

Advancing Cancer Research: Current Knowledge on Cutaneous Neoplasia.

Skin cancers require a multidisciplinary approach. The updated guidelines introduce new insights into the management of these diseases. Melanoma (MM), the third most common skin cancer, a malignant melanocytic tumor, which is classified into four major histological subtypes, continues to have the potential to be a lethal disease. The mortality-incidence ratio is higher in Eastern European countries compared to Western European countries, which shows the need for better prevention and early detection in Eastern European countries. Basal cell carcinoma (BCC) and squamous cell carcinoma (cSCC) remain the top two skin cancers, and their incidence continues to grow. The gold standard in establishing the diagnosis and establishing the histopathological subtype in BCC and SCC is a skin biopsy. Sebaceous carcinoma (SeC) is an uncommon and potentially aggressive cutaneous malignancy showing sebaceous differentiation. It accounts for 0.7% of skin cancers and 3-6.7% of cancer-related deaths. Due to the rapid extension to the regional lymph nodes, SeC requires early treatment. The main treatment for sebaceous carcinoma is surgical treatment, including Mohs micrographic surgery, which has the advantage of complete margin evaluation and low recurrence rates. Primary cutaneous lymphomas (PCLs) are a heterogeneous group of lymphoproliferative diseases, with no evidence of extracutaneous determination at the moment of the diagnosis. PCLs have usually a very different evolution, prognosis, and treatment compared to the lymphomas that may secondarily involve the skin. The aim of our review is to summarize the important changes in the approach to treating melanoma, non-melanoma skin, cutaneous T and B cell lymphomas, and other types of skin cancers. For all skin cancers, optimal patient management requires a multidisciplinary approach including dermatology, medical oncology, and radiation oncology.

Primary Cutaneous B-Cell Lymphomas with Large Cell Morphology: A Practical Review.

Most primary cutaneous lymphomas consist of T-cell lymphomas or small cell lymphomas; however, the skin may also be affected by lymphomas with large cell morphology, as a primary or secondary localization. A minority of cases consist of primary cutaneous B-cell lymphomas (PCBCLs). PCBCLs are a heterogeneous group of rare neoplasms with an overlapping morphological and immunohistochemical picture of the different subtypes. Nevertheless, differential diagnosis in the setting of this group of neoplasms is mandatory to identify the correct therapy and prognosis, but it may be challenging since, due to the rarity of these neoplasms, they may not always be familiar to pathologists. Indeed, immunohistochemistry may not be enough to distinguish the different histotypes, which overlap in immunohistochemical features. Furthermore, the ever-increasing knowledge of the molecular features of systemic B-cell lymphomas, such as gene rearrangements with clinical significance, has led in recent years to further investigation into the molecular landscape of PCBCLs with large cell morphology. This work aimed to provide a practical diagnostic guide for pathologists dealing with primary cutaneous large B-cell lymphomas.

Palliative Radiation Therapy for Treatment of Cutaneous T-cell Lymphoma in a Double Yellow-headed Amazon Parrot (Amazona oratrix).

A 17-year-old captive female double yellow-headed Amazon parrot (Amazona oratrix) was presented to the Kansas State University Zoological Medicine Service (Manhattan, KS, USA) for a 2-month history of a left sided facial swelling. On examination, a red, raised mass was noted on the left side of the face. A whole-body computed tomography scan of the bird was performed to assess the extent of the mass and evaluate the patient for obvious evidence of disseminated disease. No systemic involvement was detected, and the swelling was localized to the cutaneous and subcutaneous tissues overlying the left rhamphotheca. Two punch biopsies were collected, and histopathology was consistent with cutaneous lymphoma, with strong positive CD3 staining congruous with a T-cell origin. Because of a lack of evidence for disseminated disease, the authors elected to pursue localized radiation therapy, and a single fraction of 8 Gray was administered. The swelling had resolved by the time of the recheck examination 4 weeks post-radiation therapy, and the patient remained clinically normal 52 weeks after radiation therapy.

Primary cutaneous anaplastic large-cell lymphoma with aberrant cytokeratin expression: An unusual mimicker of poorly differentiated carcinomas.

An 81-year-old male presented with a rapidly growing cheek nodule. Biopsy revealed a dermal infiltrate of large atypical cells, some exhibiting a horseshoe-shaped nucleus. Immunohistochemistry revealed positivity for CD4, CD3, CD45, and CD30 (>95%). Melanocytic markers, cytotoxic markers, CD20, CD56, ALK1, synaptophysin, CD1a, and ETS-related gene (ERG) were negative. Notably, there was weak but diffuse expression of pan-cytokeratin (AE1/AE3) and Oscar keratin. There was also a weak expression of epithelial membrane antigen (EMA). CAM 5.2, p40, and IRF4/DUSP22 rearrangement were negative. Further staging revealed skin-limited disease. A diagnosis of primary cutaneous anaplastic large-cell lymphoma (PC-ALCL) was rendered. We present a rare case of cytokeratin positive PC-ALCL, a finding never reported in the literature. Both PC-ALCL and systemic ALCL (S-ALCL) evoke a broad differential. CD45, EMA, and cytokeratin stains help differentiate from metastatic carcinomas. There have been rare prior reports of cytokeratin expression in S-ALCL, which tend to stain with an unusual cytoplasmic and membranous pattern like our case, have variable co-expression of EMA, and null T-cell phenotypes. These show the significant diagnostic challenges that can arise in differentiating ALCL from metastatic or primary skin carcinomas. Awareness, careful attention to morphology (e.g., hallmark cells), and considering routine CD30 can help lead the pathologist to the correct diagnosis.

Cutaneous metastasis of primary diffuse large B-cell lymphoma of the central nervous system developing 4 years after complete remission: Diagnosis confirmed by comparison of clones.

B-cell lymphoma of the central nervous system (CNS) is a rare malignancy with diffuse large B-cell lymphoma (DLBCL) variant being most common. Although DLBCL has a high propensity to relapse locally within the CNS, only a few cases of cutaneous metastasis have been described in the literature. We present a unique case of cutaneous metastasis of a primary DLBCL of the CNS in a 79-year-old man who was in clinical remission for 4 years until presenting with a lesion in the left adrenal gland and cutaneous nodules on the left flank. Skin biopsy specimen revealed a diffuse dermal infiltrate of atypical B-cell lymphocytes with expression of CD20, BCL-2, BCL-6, and MUM-1, suggestive of DLBCL. For differentiation between another primary or a recurrent process, immunoglobulin kappa (IgK) light chain gene rearrangement was performed and demonstrated that the DLBCL of the skin and CNS were of the same clonal origin. Restaging computerized tomography after initiating chemotherapy and daily ibrutinib showed complete resolution of the left adrenal mass and resolving cutaneous lesions. Our case demonstrates the rare, late cutaneous metastasis of DLBCL of the CNS and highlights the importance of genetic testing for the distinction between the primary and secondary lesions.

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.

Primary cutaneous gamma/delta T-cell lymphoma in Taiwan: A series of six cases with frequent solitary presentation and relatively indolent behavior.

BACKGROUND: Primary cutaneous gamma/delta T-cell lymphoma (PCDG-TCL) is aggressive, frequently presenting as multiple plaques, tumors, and/or subcutaneous nodules. METHODS: In this study, we conducted a retrospective study in a tertiary center in Taiwan to characterize this rare tumor. RESULTS: We identified six patients. Five presented with a solitary lesion, including two with clinical impression of epidermal inclusion cyst or lipoma. Two of four evaluable cases exhibited epidermotropism, with one mimicking Pautrier microabscess. The neoplastic cells were pleomorphic and mostly medium- to large-sized. In all cases, the neoplastic cells expressed T-cell receptor (TCR)-γ and/or TCR-δ, with four co-expressing ßF1. Two of these ßF1+ cases co-expressed TCR-γ but not TCR-δ (two different clones). All were negative for Epstein-Barr virus (EBV), low stage, and treated with radiotherapy alone or combined chemotherapy and radiotherapy. In two patients, lymphoma relapsed in 3 and 7 months, respectively, and one patient died of the disease in 7 months. Four other patients were free of disease for 6 to 126 months. CONCLUSION: PCGD-TCL cases in Taiwan are more commonly solitary, frequently with indolent courses. The two currently available TCR-δ clones alone might be insufficient to detect all tumors.

Pediatric Cutaneous Hematologic Disorders: Cutaneous Lymphoma and Leukemia Cutis-Experience of a Tertiary-Care Pediatric Institution and Review of the Literature.

BACKGROUND: Cutaneous hematologic malignancies are rare in children, and the literature about them is still sparse. OBJECTIVE: The purpose of our study was to report our experience with pediatric cases of cutaneous hematologic disorders and describe their clinical and histological features. METHODS: Data were retrospectively collected from the histopathologic database of the CHU Sainte-Justine, University of Montreal, Montreal, Canada. All patients up to 18 years of age with a diagnosis of a primary cutaneous lymphoma (including lymphomatoid papulosis), secondary cutaneous lymphoma or cutaneous manifestations of leukemia, followed from 1980 to 2019 at our center were reviewed. RESULTS: Thirty-six patients were included. Age at presentation ranged from birth to 18 years of age (mean 7.83 ± 5.16; median 7.0). Ten different hematologic disorders were identified according to the WHO-EORTC classifications: lymphomatoid papulosis (10 cases), mycosis fungoides (6 cases), anaplastic large cell lymphoma (4 cases), pre-B acute lymphoid leukemia (5 cases), primary cutaneous marginal zone B-cell lymphoma (4 cases), primary cutaneous CD4+medium T-cell lymphoproliferative disorder (1 case), extranodal NK/T-cell lymphoma (1 case), hydroa vacciniforme-like lymphoproliferative disorder (1 case), B-cell lymphoblastic lymphoma (1 case) and acute myeloid leukemia (3 cases). CONCLUSION: The most common subtype of cutaneous hematologic disease in our single institution study was lymphomatoid papulosis (type A and type C), followed by mycosis fungoides. Recognition of this large clinical and histological spectrum by dermatologists is important because diagnosis is often established by biopsy of skin lesions, even in secondary cutaneous cases. Moreover, the clinicopathological correlation is of utmost importance for the final diagnosis of those pathologies.

Surgical, Dermatological and Morphopathological Considerations in the Diagnosis and Treatment of Cutaneous Lymphoproliferative Tumors, Primary CD4.

Primary cutaneous lymphomas are a heterogeneous group of T-cell (CTCL) and B-cell lymphomas (CBCL) developing in the skin and without signs of extracutaneous disease at the time of diagnosis. The term "primary small/medium CD4+ T-cell lymphoma" was changed to "primary small/medium cutaneous CD4+ lymphoproliferative disorder" due to its indolent clinical behavior and uncertain malignant potential. This paper presents a rare case of primary cutaneous lymphoma with small to medium CD4+ T-cells. A 37-year-old patient presented with a tumor in the frontal region that had occurred approximately 8-9 months earlier. The tumor had a diameter of about 8-9 mm, well demarcated macroscopically, it was round in shape, about 6-7 mm high, pink in color, firm in consistency and painless during palpation. Surgical excision of the tumor was performed with a margin of safety of 8 mm and deep to the level of the frontal muscle fascia. The histopathological examination supported the diagnosis of cutaneous lymphoproliferation with a nodular disposition in the reticular dermis and extension around the follicular epithelia and sweat glands, composed mainly of dispersed medium-large lymphocytes. Additional immunohistochemical examination was requested. Immunohistochemical examination confirmed the diagnosis of "primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder." Patient monitoring was carried out through clinical dermatological controls at 3, 6, and 12 months. After one year, a cranio-cerebral MRI was performed. For the following 5 years, an annual dermatological examination accompanied by cranio-cerebral MRI, blood count, and pulmonary X-ray were recommended. Similarly to all solitary skin lesions, the prognosis is excellent in this case, the only treatment being surgical excision.

[Unilocular cutaneous lymphoma : the hand and the blade]. / Cas clinique. Le lymphome cutané uniloculaire : la main et la lame.

Mycosis fungoides (MF) is the most frequent form of cutaneous lymphomas. MF is known as the great mimicker. The tumour d'emblee form is an exceptional presentation, for which there is no precise treatment guidance. A 45-year old man presented with tumoral MF on the dorsal side of his right hand with an extension to the forefinger. After the histological, immunohistological and the TCR monoclonality proof of MF, different topical and systemic treatments have been administered. As none of these treatments provided satisfying clinical responses, a surgical excision was finally proposed, with a very good clinical outcome and no recurrence observed after 2 months. Although exceptional in the event of an MF in general, localized tumoral forms of MF could readily benefit from a surgical excision.

: Le mycosis fongoïde (MF) est le lymphome cutané le plus fréquent. Il est notamment connu pour pouvoir se manifester sous différentes formes cliniques, dont une forme tumorale d'emblée et uniloculaire, rarissime. La prise en charge spécifique de cette forme n'est pas codifiée et se base sur les mêmes principes que pour le traitement d'un MF classique. Un homme de 45 ans s'est présenté avec un MF tumoral d'emblée et uniloculaire de la face dorsale de la main droite, avec une extension vers l'index. Après confirmation du diagnostic par histologie, immunohistochimie et biologie moléculaire en 2015, il a reçu différents traitements topiques et systémiques, sans résultats probants. Devant l'échec des multiples options thérapeutiques, une excision chirurgicale a été proposée en deux temps, avec une rémission complète à 2 mois. Quoique exceptionnelle pour cette pathologie, la chirurgie reste une option devant un MF d'emblée tumoral et uni- voire pauci-loculaire, avec une excellente réponse dans ce cas-ci.

Single-cell RNA sequencing reveals markers of disease progression in primary cutaneous T-cell lymphoma.

BACKGROUND: In early-stage mycosis fungoides (MF), the most common primary cutaneous T-cell lymphoma, limited skin involvement with patches and plaques is associated with a favorable prognosis. Nevertheless, approximately 20-30% of cases progress to tumors or erythroderma, resulting in poor outcome. At present, factors contributing to this switch from indolent to aggressive disease are only insufficiently understood. METHODS: In patients with advanced-stage MF, we compared patches with longstanding history to newly developed plaques and tumors by using single-cell RNA sequencing, and compared results with early-stage MF as well as nonlesional MF and healthy control skin. RESULTS: Despite considerable inter-individual variability, lesion progression was uniformly associated with downregulation of the tissue residency markers CXCR4 and CD69, the heat shock protein HSPA1A, the tumor suppressors and immunoregulatory mediators ZFP36 and TXNIP, and the interleukin 7 receptor (IL7R) within the malignant clone, but not in benign T cells. This phenomenon was not only found in conventional TCR-αß MF, but also in a case of TCR-γδ MF, suggesting a common mechanism across MF subtypes. Conversely, malignant cells in clinically unaffected skin from MF patients showed upregulation of these markers. CONCLUSIONS: Our data reveal a specific panel of biomarkers that might be used for monitoring MF disease progression. Altered expression of these genes may underlie the switch in clinical phenotype observed in advanced-stage MF.