Detection of wildtype Merkel cell polyomavirus genomic sequence and VP1 transcription in a subset of Merkel cell carcinoma.

AIMS: Merkel cell carcinoma (MCC) is frequently caused by the Merkel cell polyomavirus (MCPyV). Characteristic for these virus-positive (VP) MCC is MCPyV integration into the host genome and truncation of the viral oncogene Large T antigen (LT), with full-length LT expression considered as incompatible with MCC growth. Genetic analysis of a VP-MCC/trichoblastoma combined tumour demonstrated that virus-driven MCC can arise from an epithelial cell. Here we describe two further cases of VP-MCC combined with an adnexal tumour, i.e. one trichoblastoma and one poroma. METHODS AND RESULTS: Whole-genome sequencing of MCC/trichoblastoma again provided evidence of a trichoblastoma-derived MCC. Although an MCC-typical LT-truncating mutation was detected, we could not determine an integration site and we additionally detected a wildtype sequence encoding full-length LT. Similarly, Sanger sequencing of the combined MCC/poroma revealed coding sequences for both truncated and full-length LT. Moreover, in situ RNA hybridization demonstrated expression of a late region mRNA encoding the viral capsid protein VP1 in both combined as well as in a few cases of pure MCC. CONCLUSION: The data presented here suggest the presence of wildtype MCPyV genomes and VP1 transcription in a subset of MCC.

Efficacy of imiquimod in the management of lentigo maligna.

BACKGROUND: Lentigo maligna (LM) is a melanocytic proliferation occurring on photo-exposed skin that may progress to LM melanoma. Surgery is recommended as first-line treatment. Excision margins of 5-10 mm remain, without international consensus. Several studies have shown that imiquimod, an immunomodulator, induces LM regression. This study investigated the effect of imiquimod versus placebo in neoadjuvant settings. PATIENTS AND METHODS: We performed a prospective, randomized, multicentre, phase III clinical study. Patients were randomly assigned in 1:1 ratio to receive imiquimod or placebo for 4 weeks, followed by LM excision 4 weeks after the last application of imiquimod or placebo. The primary endpoint was extra-lesional excision, with a 5 mm margin from the residual pigmentation after imiquimod or vehicle. Secondary endpoints included the gain on the surface removed between the two groups; number of revision surgeries to obtain extra-lesional excisions; relapse-free time; and number of complete remissions after treatment. RESULTS: A total of 283 patients participated in this study; 247 patients, 121 patients in the placebo group and 126 in the imiquimod group, accounted for the modified ITT population. The first extralesional extirpation was performed in 116 (92%) imiquimod patients and in 102 (84%) placebo patients; the difference was not significant (p = 0.0743). Regarding the surface of LM, imiquimod reduced the LM surface (4.6-3.1 cm2 ) significantly (p < 0.001) more compared to the placebo (3.9-4.1 cm2 ). CONCLUSION: Imiquimod reduces the lentigo maligna surface after 1 month of treatment, without a higher risk of intralesional excision and with a positive aesthetic outcome.

Diagnostic accuracy of a panel of immunohistochemical and molecular markers to distinguish Merkel cell carcinoma from other neuroendocrine carcinomas.

Merkel cell carcinoma is a rare neuroendocrine carcinoma of the skin mostly induced by Merkel cell polyomavirus integration. Cytokeratin 20 (CK20) positivity is currently used to distinguish Merkel cell carcinomas from other neuroendocrine carcinomas. However, this distinction may be challenging in CK20-negative cases and in cases without a primary skin tumor. The objectives of this study were first to evaluate the diagnostic accuracy of previously described markers for the diagnosis of Merkel cell carcinoma and second to validate these markers in the setting of difficult-to-diagnose Merkel cell carcinoma variants. In a preliminary set (n = 30), we assessed optimal immunohistochemical patterns (CK20, thyroid transcription factor 1 [TTF-1], atonal homolog 1 [ATOH1], neurofilament [NF], special AT-rich sequence-binding protein 2 [SATB2], paired box protein 5, terminal desoxynucleotidyl transferase, CD99, mucin 1, and Merkel cell polyomavirus-large T antigen) and Merkel cell polyomavirus load thresholds (real-time PCR). The diagnostic accuracy of each marker was then assessed in a validation set of 103 Merkel cell carcinomas (9 CK20-negative cases and 15 cases without a primary skin tumor) and 70 extracutaneous neuroendocrine carcinoma cases. The most discriminant markers for a diagnosis of Merkel cell carcinoma were SATB2, NF expression, and Merkel cell polyomavirus DNA detection (positive likelihood ratios: 36.6, 44.4, and 28.2, respectively). Regarding Merkel cell carcinoma variants, cases without a primary skin tumor retained a similar immunohistochemical  profile and CK20-negative tumors displayed a different profile (decrease frequency of NF and SATB2 expression), but Merkel cell polyomavirus DNA remained detected (78% of cases by qPCR). Moreover, 8/9 (89%) CK20-negative Merkel cell carcinoma cases but only 3/61 (5%) CK20-negative extracutaneous neuroendocrine cases were positive for at least one of these markers. In conclusion, detection of SATB2 and NF expression and Merkel cell polyomavirus DNA helps distinguish between Merkel cell carcinoma classical and variant cases and extracutaneous neuroendocrine carcinomas.

Morphologic and immunophenotypical features distinguishing Merkel cell polyomavirus-positive and negative Merkel cell carcinoma.

In 2008, Feng et al. identified Merkel cell polyomavirus integration as the primary oncogenic event in ~80% of Merkel cell carcinoma cases. The remaining virus-negative Merkel cell carcinoma cases associated with a high mutational load are most likely caused by UV radiation. The current study aimed to compare the morphological and immunohistochemical features of 80 virus-positive and 21 virus-negative Merkel cell carcinoma cases. Microscopic evaluation revealed that elongated nuclei-similar to the spindle-shape variant of small cell lung cancer-were less frequent in Merkel cell polyomavirus-positive Merkel cell carcinoma compared to the virus-negative subset (p = 0.005). Moreover, virus-negative cases more frequently displayed a "large-cell neuroendocrine carcinoma" phenotype with larger cell size (p = 0.0026), abundant cytoplasm (p = 4×10-7) and prominent nucleoli (p = 0.002). Analysis of immunohistochemical data revealed frequent positivity for thyroid transcription factor 1 and cytokeratin 7, either absence or overexpression of p53, as well as frequent lack of neurofilament expression in virus-negative cases. By contrast, cytokeratin 8, 18 and 20 and a CD99 with a dot pattern as well as high EMA expression were identified as characteristic features of virus-positive Merkel cell carcinoma. In particular, the CD99 dot-like expression pattern was strongly associated with presence of the Merkel cell polyomavirus in Merkel cell carcinoma (sensitivity = 81%, specificity = 90%, positive likelihood ratio = 8.08). To conclude, virus-positive and -negative Merkel cell carcinoma are characterized by distinct morphological and immunohistochemical features, which implies a significant difference in tumor biology and behavior. Importantly, we identified the CD99 staining pattern as a marker indicating the virus status of this skin cancer.

Merkel cell carcinomas infiltrated with CD33+ myeloid cells and CD8+ T cells are associated with improved outcome.

BACKGROUND: Merkel cell carcinoma (MCC) is a rare tumor of the skin that has an aggressive behavior. Immunity is the main regulator of MCC development, and many interactions between lymphocytes and tumor cells have been proven. However, the impact of tumor-infiltrating myeloid cells needs better characterization. OBJECTIVE: To characterize tumor-infiltrating myeloid cells in MCC and their association with other immune effectors and patient outcome. METHODS: MCC cases were reviewed from an ongoing prospective cohort study. In all, 103 triplicate tumor samples were included in a tissue microarray. Macrophages, neutrophils, and myeloid-derived suppressor cells were characterized by the following markers: CD68, CD33, CD163, CD15, CD33, and human leukocyte antigen-DR. Associations of these cell populations with programmed cell death ligand 1 expression, CD8 infiltrates, and vascular density were assessed. Impact on survival was analyzed by log-rank tests and a Cox multivariate model. RESULTS: The median density of macrophages was 216 cells/mm2. CD68+ and CD33+ macrophage densities were associated with CD8+ T-cell infiltrates and programmed cell death ligand 1 expression. In addition, MCC harboring CD8+ T cell infiltrates and brisk CD33+ myeloid cell infiltrates were significantly and independently associated with improved outcomes (recurrence-free and overall survival). LIMITATIONS: Sampling bias and the retrospective design were potential study limitations. CONCLUSION: Infiltration of CD33+ myeloid cells and CD8+ T lymphocytes defines a subset of MCC associated with improved outcome.

Differentiating Merkel cell carcinoma of lymph nodes without a detectable primary skin tumor from other metastatic neuroendocrine carcinomas: The ELECTHIP criteria.

BACKGROUND: Merkel cell carcinoma (MCC) can present as a cutaneous tumor or a lymph node metastasis without a primary tumor. MCC presenting without a primary tumor (MCCWOPT) can be misinterpreted on histologic examination as lymph node metastasis (LNM) from another neuroendocrine carcinoma (LNMNEC). However, this distinction is crucial for therapeutic management. OBJECTIVE: To determine the discriminative criteria for the differential diagnosis of MCCWOPT, LNM from cutaneous MCC, and LNMNECs. METHODS: Clinical, morphologic, and immunohistochemical data (expression of cytokeratins AE1, AE3, 7, 19, and 20; chromogranin A, synaptophysin, thyroid transcription factor-1 [TTF-1]), as well as the presence of Merkel cell polyomavirus (by immunohistochemistry and PCR) were compared in patients with MCCWOPT (n = 17), LNM from a cutaneous MCC (n = 11), and LNMNEC (n = 20; 8 lung, 7 thyroid, 3 digestive tract, 2 other). RESULTS: MCC (including MCCWOPT and LNM from a cutaneous MCC) differed from LNMNEC by 7 discriminative criteria: 1) elderly age, 2) location of the tumor, 3) extent of the disease, 4) cytokeratin expression, 5) TTF-1 expression, 6) histologic type, and 7) Merkel cell polyomavirus detection, summarized under the acronym ELECTHIP. All MCC patients had ≥5 of the ELECTHIP criteria, whereas all patients with LNMNEC (except 1) had <3 criteria. LIMITATIONS: The discriminant ability of the ELECTHIP criteria should be validated in a second independent set. CONCLUSION: MCCWOPT can be distinguished from other LNMNEC by the ELECTHIP criteria.

[Gastro-intestinal neuroectodermal tumor (GNET): A case report of a small intestine tumor with hepatic metastases]. / Tumeur neuroectodermique gastro-intestinale (GNET) : à propos d'un cas de tumeur du grêle avec métastases hépatiques.

The gastro-intestinal neuroectodermal tumor (GNET) is a rare sarcoma of the digestive tract, which was recently recognised. The knowledge of the morphological, immunohistochemical and molecular diagnostic criteria is necessary to not mistake it for the metastasis of a melanoma or for another sarcoma of the digestive tract as the gastro-intestinal clear cells sarcoma or the malignant peripheral nervous system tumor (MPNST). We report the case of a 41-year-old patient with a GNET of the small intestine with hepatic metastasis. The histological examination showed a diffuse proliferation of epithelioid cells, which only express PS100. The presence EWSR1-ATF1 gene fusions with any melanocytic differentiation leads to the diagnosis of GNET.

Sunscreens.

Sunscreens have become since more than 40 years the most popular means of protection against UV radiation (UVR) in Western countries. Organic and inorganic filters with different absorption spectrum exist. They filter or scatter UVR. Protection from UVB is quantified as a minimal erythema dose-based sun protection factor. UVA protection testing is less standardized: Persistent pigment darkening and critical wavelength are currently used methods. Marketing and labeling of sunscreens underlay national regulation which explains major differences between the European and the US sunscreen market. Sunscreens are most performing in sunburn prevention. Broad spectrum UVB and UVA protection and regular application in sufficient amounts are essential for prevention of skin cancers, UV-induced immunosuppression, and skin aging. A significant benefit from regular sunscreen use has not yet been demonstrated for primary prevention of basal cell carcinoma and melanoma. Concerning the prevention of actinic keratoses, squamous cell carcinomas, and skin aging, the effect of sunscreens is significant, but it remains incomplete. Some organic UV filters (PABA derivatives, cinnamates, benzophenones, and octocrylene) have been described to cause photoallergy. Percutaneous absorption and endocrine disrupting activity of small-sized organic and nano-sized inorganic UV filters have been reported. On lesional skin and in pediatric settings, these products should be used with caution. Cutaneous vitamin D synthesis depending on skin-carcinogenic UVB radiation, the potential risk of vitamin D deficiency by sunscreen use has become a major subject of public health debate. Sunscreens indeed impair vitamin D synthesis if they are used in the recommended amount of 2 mg/cm2, but not in lesser thickness below 1.5 mg/cm2 that corresponds better to what users apply in real life conditions. Large molecular last generation UVB-UVA broad spectrum sunscreens have a better benefit-risk ratio than former organic filters: They offer better protection in the UVA band, they are non toxic and non allergenic. A better outcome of sunscreen efficacy especially in primary skin cancer prevention may be achieved with these molecules.

Real-life efficacy of immunotherapy for Sézary syndrome: a multicenter observational cohort study.

Background: Sézary syndrome is an extremely rare and fatal cutaneous T-cell lymphoma (CTCL). Mogamulizumab, an anti-CCR4 monoclonal antibody, has recently been associated with increased progression-free survival in a randomized clinical trial in CTCL. We aimed to evaluate OS and prognostic factors in Sézary syndrome, including treatment with mogamulizumab, in a real-life setting. Methods: Data from patients with Sézary (ISCL/EORTC stage IV) and pre-Sézary (stage IIIB) syndrome diagnosed from 2000 to 2020 were obtained from 24 centers in Europe. Age, disease stage, plasma lactate dehydrogenases levels, blood eosinophilia at diagnosis, large-cell transformation and treatment received were analyzed in a multivariable Cox proportional hazard ratio model. This study has been registered in ClinicalTrials (SURPASSe01 study: NCT05206045). Findings: Three hundred and thirty-nine patients were included (58% men, median age at diagnosis of 70 years, Q1-Q3, 61-79): 33 pre-Sézary (9.7% of 339), 296 Sézary syndrome (87.3%), of whom 10 (2.9%) had large-cell transformation. One hundred and ten patients received mogamulizumab. Median follow-up was 58 months (95% confidence interval [CI], 53-68). OS was 46.5% (95% CI, 40.6%-53.3%) at 5 years. Multivariable analysis showed that age ≥ 80 versus <50 (HR: 4.9, 95% CI, 2.1-11.2, p = 0.001), and large-cell transformation (HR: 2.8, 95% CI, 1.6-5.1, p = 0.001) were independent and significant factors associated with reduced OS. Mogamulizumab treatment was significantly associated with decreased mortality (HR: 0.34, 95% CI, 0.15-0.80, p = 0.013). Interpretation: Treatment with mogamulizumab was significantly and independently associated with decreased mortality in Sézary syndrome. Funding: French Society of Dermatology, Swiss National Science Foundation (IZLIZ3_200253/1) and SKINTEGRITY.CH collaborative research program.

Clostridium difficile infection and immune checkpoint inhibitor-induced colitis in melanoma: 18 cases and a review of the literature.

Immunotherapy has become the standard of care for several types of cancer, such as melanoma. However, it can induce toxicity, including immune checkpoint inhibitor-induced colitis (CIC). CIC shares several clinical, histological, biological, and therapeutic features with inflammatory bowel disease (IBD). Clostridium difficile infection (CDI) can complicate the evolution of IBD. We aimed to characterize the association between CDI and CIC in patients treated with anti-CTLA-4 and anti-PD-1 for melanoma. Patients from nine centers treated with anti-CTLA-4 and anti-PD-1 for melanoma and presenting with CDI from 2010 to 2021 were included in this retrospective cohort. The primary endpoint was the occurrence of CIC. The secondary endpoints were findings allowing us to characterize CDI. Eighteen patients were included. Eleven were treated with anti-PD-1, four with anti-CTLA-4, and three with anti-PD-1 in combination with anti-CTLA-4. Among the 18 patients, six had isolated CDI and 12 had CIC and CDI. Among these 12 patients, eight had CIC complicated by CDI, three had concurrent CIC and CDI, and one had CDI followed by CIC. CDI was fulminant in three patients. Endoscopic and histological features did not specifically differentiate CDI from CIC. Nine of 11 patients required immunosuppressive therapy when CDI was associated with CIC. In nine cases, immunotherapy was discontinued due to digestive toxicity. CDI can be isolated or can complicate or reveal CIC. CDI in patients treated with immunotherapy shares many characteristics with CDI complicating IBD. Stool tests for Clostridium difficile should be carried out for all patients with diarrhea who are being treated with immunotherapy.

Distinct Regulation of EZH2 and its Repressive H3K27me3 Mark in Polyomavirus-Positive and -Negative Merkel Cell Carcinoma.

Merkel cell carcinoma (MCC) is an aggressive skin cancer for which Merkel cell polyomavirus integration and expression of viral oncogenes small T and Large T have been identified as major oncogenic determinants. Recently, a component of the PRC2 complex, the histone methyltransferase enhancer of zeste homolog 2 (EZH2) that induces H3K27 trimethylation as a repressive mark has been proposed as a potential therapeutic target in MCC. Because divergent results have been reported for the levels of EZH2 and trimethylation of lysine 27 on histone 3, we analyzed these factors in a large MCC cohort to identify the molecular determinants of EZH2 activity in MCC and to establish MCC cell lines' sensitivity to EZH2 inhibitors. Immunohistochemical expression of EZH2 was observed in 92% of MCC tumors (156 of 170), with higher expression levels in virus-positive than virus-negative tumors (P = 0.026). For the latter, we showed overexpression of EZHIP, a negative regulator of the PRC2 complex. In vitro, ectopic expression of the large T antigen in fibroblasts led to the induction of EZH2 expression, whereas the knockdown of T antigens in MCC cell lines resulted in decreased EZH2 expression. EZH2 inhibition led to selective cytotoxicity on virus-positive MCC cell lines. This study highlights the distinct mechanisms of EZH2 induction between virus-negative and -positive MCC.

Guidelines for the diagnosis and treatment of Merkel cell carcinoma - Cutaneous Oncology Group of the French Society of Dermatology.

BACKGROUND: Merkel cell carcinoma (MCC) is a rare neuroendocrine tumor of the skin. The epidemiological factors strongly associated with this tumor are: age over 65 years, fair skin, chronic sun exposure and immune suppression. Data are sparse in the literature and many questions remain unanswered regarding the diagnosis and treatment of this tumor. OBJECTIVE: To provide clinical practice guidelines for the diagnosis and treatment of MCC. METHOD: The literature data were analyzed and the current American and German practice guidelines were compared. Consensus items between these two guidelines were adopted as recommendations. Regarding discordant points, a formalized expert consensus process was devised. The guidelines were then written up by an editorial panel and validated by the Cutaneous Oncology Group of the French Society of Dermatology. RESULTS: The guidelines were drawn up according to three levels of scientific evidence: (a) complete agreement between the American and German guidelines; (b) the results of the formalized expert consensus process; and (c) the expert opinion of the steering group, based on analysis of the available evidence. The guidelines presented here are up-to-date recommendations on the clinical and pathological procedures for MCC diagnosis, staging, surgical treatment, sentinel node biopsy, radiotherapy and follow-up. CONCLUSION: These guidelines for diagnosis and treatment of MCC should standardize MCC management, which may not be optimal in France today.

Investigation of the RB1-SOX2 axis constitutes a tool for viral status determination and diagnosis in Merkel cell carcinoma.

MCC (Merkel cell carcinoma) is an aggressive neuroendocrine cutaneous neoplasm. Integration of the Merkel cell polyomavirus (MCPyV) is observed in about 80% of the cases, while the remaining 20% are related to UV exposure. Both MCPyV-positive and -negative MCCs-albeit by different mechanisms-are associated with RB1 inactivation leading to overexpression of SOX2, a major contributor to MCC biology. Moreover, although controversial, loss of RB1 expression seems to be restricted to MCPyV-negative cases.The aim of the present study was to assess the performances of RB1 loss and SOX2 expression detected by immunohistochemistry to determine MCPyV status and to diagnose MCC, respectively.Overall, 196 MCC tumors, 233 non-neuroendocrine skin neoplasms and 70 extra-cutaneous neuroendocrine carcinomas (NEC) were included. SOX2 and RB1 expressions were assessed by immunohistochemistry in a tissue micro-array. Diagnostic performances were determined using the likelihood ratio (LHR).RB1 expression loss was evidenced in 27% of the MCC cases, 12% of non-neuroendocrine skin tumors and 63% of extra-cutaneous NEC. Importantly, among MCC cases, RB1 loss was detected in all MCPyV(-) MCCs, while MCPyV( +) cases were consistently RB1-positive (p < 0.001). SOX2 diffuse expression was observed in 92% of the MCC cases and almost never observed in non-neuroendocrine skin epithelial neoplasms (2%, p < 0.0001, LHR + = 59). Furthermore, SOX2 diffuse staining was more frequently observed in MCCs than in extra-cutaneous NECs (30%, p < 0.001, LHR + = 3.1).These results confirm RB1 as a robust predictor of MCC viral status and further suggest SOX2 to be a relevant diagnostic marker of MCC.

Merkel Cell Polyomavirus‒Negative Merkel Cell Carcinoma Originating from In Situ Squamous Cell Carcinoma: A Keratinocytic Tumor with Neuroendocrine Differentiation.

Although virus-negative Merkel cell carcinoma (MCC) is characterized by a high frequency of UV-induced mutations, the expression of two viral oncoproteins is regarded as a key mechanism driving Merkel cell polyomavirus‒positive MCC. The cells in which these molecular events initiate MCC oncogenesis have yet not been identified for both MCC subsets. A considerable proportion of virus-negative MCC is found in association with squamous cell carcinoma (SCC), suggesting (i) coincidental collision, (ii) one providing a niche for the other, or (iii) one evolving from the other. Whole-exome sequencing of four combined tumors consisting of SCC in situ and Merkel cell polyomavirus‒negative MCC showed many mutations shared between SCC and MCC in all cases, indicating a common ancestry and thereby a keratinocytic origin of these MCCs. Moreover, analyses of the combined cases as well as of pure SCC and MCC suggest that RB1 inactivation in SCC facilitates MCC development and that epigenetic changes may contribute to the SCC/MCC transition.