Recurrent FOXK1::GRHL and GPS2::GRHL fusions in trichogerminoma.

We report 21 cases of trichogerminoma harbouring previously undescribed FOXK1::GRHL1/2 or GPS2::GRHL1/2/3 in-frame fusion transcripts. Microscopic examination of a preliminary set of five cases revealed well-delimitated tumours located in the dermis with frequent extension to the subcutaneous tissue. Tumours presented a massive and nodular architecture and consisted of a proliferation of basaloid cells. A biphasic pattern sometime resulting in tumour cell nests ('cell balls') was present. Immunohistochemistry demonstrated the expression of cytokeratins (CKs) 15, 17, and PHLDA1. In addition, numerous CK20-positive Merkel cells were detected. RNA sequencing (RNA-seq) revealed a FOXK1::GRHL1 chimeric transcript in three cases and a FOXK1::GRHL2 fusion in two cases. In a second series for validation (n = 88), FOXK1::GRHL1/2 fusion transcripts were detected by RT-qPCR or FISH in an additional 12 trichogerminomas and not in any other follicular tumour entities or basal cell carcinoma cases (n = 66). Additional RNA-seq analysis in trichogerminoma cases without detected FOXK1::GRHL1/2 rearrangements revealed GPS2::GRHL1 fusion transcripts in two cases, GPS2::GRHL2 in one case, and GPS2::GRHL3 fusion transcript in one case. Therefore, our study strongly suggests that GRHL1/2/3 gene rearrangements might represent the oncogenic driver in trichogerminoma, a subset of follicular tumours characterized by immature features and numerous Merkel cells. © 2022 The Pathological Society of Great Britain and Ireland.

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.

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.

Measurement of histological clearance margins in basal cell carcinoma.

AIMS: Basal cell carcinoma (BCC) is a common cancer, with a high risk of local recurrence. A quantifiable measurement of the histological margins of BCC in excisions is a recurrent demand of clinicians; however, there are currently no international guidelines indicating its value. METHODS AND RESULTS: A questionnaire validated by four experts in dermatopathology and formatted under a 'Google Forms'-type interface was sent by e-mail to physicians specializing in surgical pathology or dermatopathology and practising in France from 20 March 2018 to 20 May 2018. The results were compared between subgroups according to age and subspecialisation, especially dermatopathology. The questionnaire was completed by 225 practitioners. Microscopic margins were systematically measured in 77.3% of cases, sometimes in 19.6% and never in 3.1%. The main reason was to report factually insufficient margins (66.5%), followed by laboratory routine (45%) or clinician requests (43.1%). For 72% of respondents, the clinical or histopathological criteria did not influence their practice. The most used tool was a graduated ruler placed under a microscope (44.3% of cases). Compared to other groups, dermatopathologists measured BCC margins less systematically [only in certain situations (33.3 versus 14.9%) or never (10.5 versus 0.6%) (P < 0.001)] and used an eyepiece reticle more extensively (53.1 versus 29.8%; P = 0.0029). CONCLUSION: The measurement of histological margins in BCC is common practice in France, although there are no recommendations. Our survey suggests that it represents a way for pathologists to specify an insufficient margin and therefore the need for scar revision.

Harmonization of programmed death-ligand 1 immunohistochemistry and mRNA expression scoring in metastatic melanoma: a multicentre analysis.

AIMS: The aim of this multicentre study was to harmonize programmed death-ligand 1 (PD-L1) immunohistochemistry (IHC) and melanoma scoring. To provide a reference for PD-L1 expression independently of the IHC protocol, PD-L1 mRNA expression was compared with IHC. METHODS AND RESULTS: Standardized PD-L1 assays (22C3, 28-8, SP142, SP263) and laboratory-developed tests (QR1, 22C3) were evaluated on three IHC platforms with a training set (seven cases). mRNA expression was determined by RNAscope (CD274/PD-L1 probe) and analysed with image analysis. PD-L1 IHC findings were scored by seven blinded pathologists using the tumour proportion score (TPS), the combined positive score (CPS), and the MELscore. This method was validated by three blinded pathologists on 40 metastatic melanomas. Concordances among various antibody/platforms were high across antibodies [intraclass correlation coefficient (ICC) >0.80 for the CPS], except for SP142. Two levels of immunostaining intensity were observed: high (QR1 and SP263) and low (28-8, 22C3, and SP142). Reproducibilities across pathologists were higher for QR1 and SP263 (ICC ≥0.87 and ICC ≥0.85 for the TPS and the CPS, respectively). QR1, SP263 and 28-8 showed the highest concordance with mRNA expression. We developed a standardized method for PD-L1 immunodetection and scoring, tested on 40 metastatic melanomas. Concordances among antibodies were excellent for all criteria, and concordances among pathologists were better for the MELscore than for other scores. CONCLUSION: Harmonization of PD-L1 staining and scoring in melanomas with good concordance is achievable with the PD-L1 IHC protocols applied to other cancers; this reproducible approach can simplify daily practice.

Primary cutaneous peripheral T-cell lymphomas with a T-follicular helper phenotype: an integrative clinical, pathological and molecular case series study.

BACKGROUND: Primary cutaneous peripheral T-cell lymphomas with a T-follicular helper phenotype (pcTFH-PTCL) are poorly characterized, and often compared to, but not corresponding with, mycosis fungoides (MF), Sézary syndrome, primary cutaneous CD4+ lymphoproliferative disorder, and skin manifestations of angioimmunoblastic T-cell lymphomas (AITL). OBJECTIVES: We describe the clinicopathological features of pcTFH-PTCL in this original series of 23 patients, and also characterize these cases molecularly. METHODS: Clinical and histopathological data of the selected patients were reviewed. Patient biopsy samples were also analysed by targeted next-generation sequencing. RESULTS: All patients (15 men, eight women; median age 66 years) presented with skin lesions, without systemic disease. Most were stage T3b, with nodular (n = 16), papular (n = 6) or plaque (atypical for MF, n = 1) lesions. Three (13%) developed systemic disease and died of lymphoma. Nine (39%) patients received more than one line of chemotherapy. Histologically, the lymphomas were CD4+ T-cell proliferations, usually dense and located in the deep dermis (n = 14, 61%), with the expression of at least two TFH markers (CD10, CXCL13, PD1, ICOS, BCL6), including three markers in 16 cases (70%). They were associated with a variable proportion of B cells. Eight patients were diagnosed with an associated B-cell lymphoproliferative disorder (LPD) on biopsy, including Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphoma (n = 3), EBV+ LPD (n = 1) and monotypic plasma cell LPD (n = 4). Targeted sequencing showed four patients to have a mutated TET2-RHOAG17V association (as frequently seen in AITL) and another a TET2/DNMT3A/PLCG1/SETD2 mutational profile. The latter patient, one with a TET2-RHOA association, and one with no detected mutations, developed systemic disease and died. Five other patients showed isolated mutations in TET2 (n = 1), PLCG1 (n = 2), SETD2 (n = 1) or STAT5B (n = 1). CONCLUSIONS: Patients with pcTFH-PTCL have pathological and genetic features that overlap with those of systemic lymphoma of TFH derivation. Clinically, most remained confined to the skin, with only three patients showing systemic spread and death. Whether pcTFH-PTCL should be integrated as a new subgroup of TFH lymphomas in future classifications is still a matter of debate. What is already known about this topic? There is a group of cutaneous lymphomas that express T-follicular helper (TFH) markers that do not appear to correspond to existing World Health Organization diagnostic entities. These include mycosis fungoides, Sézary syndrome, or primary cutaneous CD4+ small/medium-sized T-cell lymphoproliferative disorder or cutaneous extensions of systemic peripheral T-cell lymphomas (PTCL) with TFH phenotype. What does this study add? This is the first large original series of patients with a diagnosis of primary cutaneous PTCL with a TFH phenotype (pcTFH-PTCL) to be molecularly characterized. pcTFH-PTCL may be a standalone group of cutaneous lymphomas with clinicopathological and molecular characteristics that overlap with those of systemic TFH lymphomas, such as angioimmunoblastic T-cell lymphoma, and does not belong to known diagnostic groups of cutaneous lymphoma. This has an impact on the treatment and follow-up of patients; the clinical behaviour needs to be better clarified in further studies to tailor patient management.

Change in lentigo maligna score assessed by in vivo reflectance confocal microscopy after 1 month of imiquimod treatment for lentigo maligna management.

BACKGROUND: Treatment of lentigo maligna (LM) is challenging because of the potential functional and esthetic surgical sequelae. Imiquimod has been proposed as a treatment for LM. Reflectance confocal microscopy (RCM) is a noninvasive method for the diagnosis of LM and margin assessment. OBJECTIVES: To compare the overall LM score (LMS) assessed by RCM before and 1 month after the start of imiquimod treatment compared to placebo and to define the immunohistochemical (IHC) profile of responders to imiquimod. METHODS: A controlled randomized study was conducted. Forty patients underwent RCM examination with calculation of the LMS at baseline and after 1 month of treatment. An IHC analysis of excised tissues was performed. RESULTS: The 1-month LMS was significantly lower in patients treated with imiquimod compared to those treated with placebo (P < .001). The criteria in the imiquimod-treated patients that demonstrated significant decrease were nonedged papillae; large, round pagetoid cells; atypical cells at the dermoepidermal junction; and follicular location of atypical cells. IHC analysis showed a higher level of interferon gamma in the resected specimens of patients responding to imiquimod (P = .04). LIMITATIONS: Sample size was small. CONCLUSION: Assessing the LMS by RCM was useful to monitor LM response to imiquimod accurately.

A High Programmed Cell Death Protein 1 Hormone Receptor Score on Skin Biopsy is Associated with Sézary Syndrome Diagnosis: A Study of 91 Patients with Erythroderma.

Erythroderma is challenging to diagnose. The aim of this single-centre retrospective study was to identify factors that can be used to improve the diagnosis of erythroderma. Among 91 patients with erythroderma, 21 were diagnosed with eczema, 17 with psoriasis, 20 with drug-induced erythroderma, 13 with erythrodermic mycosis fungoides and 20 with Sézary syndrome. Nail alterations, ear involvement, and severe scaling were significantly associated with psoriasis (p = 0.044). Fever and hypereosinophilia were associated with drug-induced erythroderma. Expression of programmed cell death protein 1 was observed in all skin biopsies. However, with Sézary syndrome, programmed cell death protein 1 expression was significantly higher than with other aetiologies. A programmed cell death protein 1 hormone receptor score (H-score) >50 was associated with Sézary syndrome (p < 0.001, sensitivity 75%, specificity 92%) as well as CXCL13 expression (p < 0.044). CD7 loss was more frequent with erythrodermic mycosis fungoides and Sézary syndrome (p = 0.022). This study reports the importance of programmed cell death protein 1 expression for the differential diagnosis of Sézary syndrome and other aetiologies, including erythrodermic mycosis fungoides.

[Impact of algorithms proposed by the Cutaneous Lymphoma French Study Group for diagnosis of cutaneous lymphoproliferations]. / Impact des algorithmes du groupe français d'étude des lymphomes cutanés (GFELC) sur le diagnostic anatomopathologique des lymphoproliférations cutanées.

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.

Cutaneous Involvement in Waldenström's Macroglobulinaemia.

Cutaneous involvement in Waldenström's macroglobulinaemia (WM) has been poorly characterized. To describe this involvement, a retrospective study of 19 patients with WM and cutaneous involvement of tumour B cells was performed. Twelve patients (group 1) had lymphoplasmacytic, non-transformed cutaneous proliferation, while in 7 cases (group 2) cutaneous involvement corresponded to histological transformation. In group 1, skin involvement was inaugural in 6 cases. The lesions were infiltrated plaques (83%), papules (25%) and tumours (42%). Four patients had a similar clinical picture (purplish, bilateral and symmetrical infiltration on the face). MYD88 L265P mutation was detected in the skin biopsy in all 6 cases tested. The 3-year specific survival rate was 88%. In group 2, cutaneous transformation occurred during the follow-up of the WM (71%). Lesions presented as ulcerated tumours (86%) of the trunk (57%) and lower limbs (57%). The 3-year specific survival rate was 22%. Skin involvement in WM has distinctive characteristics (e.g. clinical, histological, immunohistochemical, MYD88 L265P mutation).

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

AIMS: We applied the 2017 World Health Organization (WHO) classification criteria to categorise a series of 64 primary cutaneous large B-cell lymphomas (PCLBCLs), containing a majority (≥80%) of large cells and a proliferative rate of ≥40%, raising the problem of the differential diagnosis between PCLBCL, leg type (PCLBCL-LT) and primary cutaneous follicle centre lymphoma, large cell (PCFCL-LC). The aims were to determine the reproducibility and prognostic relevance of the 2017 WHO criteria. METHODS AND RESULTS: Morphology and phenotype identified 32 PCLBCLs-LT and 25 PCFCLs-LC; seven cases (11%) remained unclassified. Morphology was less reproducible than immunophenotype. Pertinent markers for the differential diagnosis were MUM1, FOXP1, CD10, and IgM. bcl-2 and bcl-6 were expressed by both PCFCLs-LC and PCLBCLs-LT at substantial levels. Neither Ki67 expression nor p63 expression was of diagnostic value. MYD88 was found to be mutated only in PCLBCLs-LT (n = 22, 69%). According to Hans/Hans modified algorithms, 23 of 25 PCFCLs-LC had germinal centre (GC) status, and the 32 PCLBCLs-LT had non-GC status. Overall survival was poorer for PCLBCLs-LT than PCFCLs-LC (P = 0.0002). Non-GC cases had poorer overall survival than GC cases (P = 0.0007). In PCLBCLs-LT, MYC expression was associated with cutaneous relapses (P = 0.014). When GC/non-GC status was applied to unclassified cases, only a single case remained discordant. CONCLUSIONS: Our results support the 2017 WHO classification criteria for PCLBCL diagnosis. The Hans modified algorithm using CD10 and MUM1 distinguished PCFCLs-LC from PCLBCLs-LT with optimal diagnostic value without requiring bcl-6 immunolabelling (poorly reproducible). Rare unclassified cases may constitute a provisionally heterogeneous subgroup for which GC/non-GC status (relevant for prognosis) may guide therapeutic decisions.

Clinical, histological and molecular predictors of metastatic melanoma responses to anti-PD-1 immunotherapy.

BACKGROUND: Prescribing anti-programmed death-1 (PD-1) immunotherapy for advanced melanoma is currently not restricted by any biomarker assessment. Determination of programmed death-ligand-1 (PD-L1)-expression status is technically challenging and is not mandatory, because negative tumours also achieve therapeutic responses. However, reproducible biomarkers predictive of a response to anti-PD-1 therapy could contribute to improving therapeutic decision-making. METHODS: This retrospective study on 70 metastatic melanoma patients was undertaken to evaluate the relationships between clinical, histological, immunohistochemical and/or molecular criteria, and the 6-month objective response rate. RESULTS: Better objective response rates were associated with metachronous metastases (P = 0.04), PD-L1 tumour- and/or immune-cell status (P = 0.01), CD163+ histiocytes at advancing edges (P = 0.009) of primary melanomas and NRAS mutation (P = 0.019). Moreover, CD163+ histiocytes at advancing edges (P = 0.04) were associated with longer progression-free survival (PFS), and metachronous metastases with longer overall survival (P = 0.02) and PFS (P = 0.049). CONCLUSIONS: Combining these reproducible biomarkers could help improve therapeutic decision-making for patients with progressive disease.

Double-hit or dual expression of MYC and BCL2 in primary cutaneous large B-cell lymphomas.

In nodal diffuse large B-cell lymphoma, the search for double-hit with MYC and BCL2 and/or BCL6 rearrangements or for dual expression of BCL2 and MYC defines subgroups of patients with altered prognosis that has not been evaluated in primary cutaneous large B-cell lymphoma. Our objectives were to assess the double-hit and dual expressor status in a cohort of 44 patients with primary cutaneous large B-cell lymphoma according to the histological subtype and to evaluate their prognosis relevance. The 44 cases defined by the presence of more than 80% of large B-cells in the dermis corresponded to 21 primary cutaneous follicle centre lymphoma with large cell morphology and 23 primary cutaneous diffuse large B-cell lymphoma, leg type. Thirty-one cases (70%) expressed BCL2 and 29 (66%) expressed MYC. Dual expressor profile was observed in 25 cases (57%) of either subtypes (n = 6 or n = 19, respectively). Only one primary cutaneous follicle centre lymphoma, large-cell case had a double-hit status (2%). Specific survival was significantly worse in primary cutaneous diffuse large B-cell lymphoma, leg type than in primary cutaneous follicle centre lymphoma, large cell (p = 0.021) and for the dual expressor primary cutaneous large B-cell lymphoma group (p = 0.030). Both overall survival and specific survival were worse for patients belonging to the dual expressor primary cutaneous diffuse large B-cell lymphoma, leg type subgroup (p = 0.001 and p = 0.046, respectively). Expression of either MYC and/or BCL2 negatively impacted overall survival (p = 0.017 and p = 0.018 respectively). As the differential diagnosis between primary cutaneous follicle centre lymphoma, large cell and primary cutaneous diffuse large B-cell lymphoma, leg type has a major impact on prognosis, dual-expression of BCL2 and MYC may represent a new diagnostic criterion for primary cutaneous diffuse large B-cell lymphoma, leg type subtype and further identifies patients with impaired survival. Finally, the double-hit assessment does not appear clinically relevant in primary cutaneous large B-cell lymphoma.

Subcutaneous Panniculitis-like T-cell Lymphoma: Immunosuppressive Drugs Induce Better Response than Polychemotherapy.

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare condition usually considered to have a favourable prognosis. However, it is not known whether polychemotherapy or immunosuppressive-based therapy is the best approach for treating SPTCL. Using data collected between 2000 and 2012 in France, we analysed clinical, biological and pathological data of 27 patients with SPTCL. Medical history revealed that 40% of patients had been previously diagnosed with an autoimmune disorder and 22% with inflammatory panniculitis. Haemophagocytic syndrome was present in 37% of cases. Autoantibodies were positive in 65% of cases. Complete remission (CR) was reached in 74% of cases. Immunosuppressive drug treatment was given in 69.5% of patients (group 1) and polychemotherapy in 30.5% (group 2). CR was 81.2% and 28.5% (p?=?0.025), respectively. Progression rate was 6.2% and 42.8% (p?=?0.067), respectively. This study suggests that immunosuppressive drugs should be considered as the first-line treatment for SPTCL.

Telomerase functions beyond telomere maintenance in primary cutaneous T-cell lymphoma.

Telomere erosion may be counteracted by telomerase. Here we explored telomere length (TL) and telomerase activity (TA) in primary cutaneous T-cell lymphoma (CTCL) by using quantitative polymerase chain reaction and interphase quantitative fluorescence in situ hybridization assays. Samples from patients with Sézary syndrome (SS), transformed mycosis fungoides (T-MF), and cutaneous anaplastic large cell lymphoma were studied in parallel with corresponding cell lines to evaluate the relevance of TL and TA as target candidates for diagnostic and therapeutic purposes. Compared with controls, short telomeres were observed in aggressive CTCL subtypes such as SS and T-MF and were restricted to neoplastic cells in SS. While no genomic alteration of the hTERT (human telomerase catalytic subunit) locus was observed in patients' tumor cells, TA was detected. To understand the role of telomerase in CTCL, we manipulated its expression in CTCL cell lines. Telomerase inhibition rapidly impeded in vitro cell proliferation and led to cell death, while telomerase overexpression stimulated in vitro proliferation and clonogenicity properties and favored tumor development in immunodeficient mice. Our data indicate that, besides maintenance of TL, telomerase exerts additional functions in CTCL. Therefore, targeting these functions might represent an attractive therapeutic strategy, especially in aggressive CTCL.

Immunohistochemistry as a potential tool for routine detection of the NRAS Q61R mutation in patients with metastatic melanoma.

BACKGROUND: It can be useful to assess the NRAS mutation status in patients with metastatic melanoma because NRAS-activating mutations confer resistance to RAF inhibitors, and NRAS-mutated patients appear to be sensitive to mitogen-activated protein kinase (MEK) inhibitors. OBJECTIVE: We aimed to assess the diagnostic accuracy of an immunohistochemistry (IHC) approach using a novel anti-NRAS (Q61R) monoclonal antibody on formalin-fixed paraffin-embedded tissue samples from patients with metastatic melanoma. METHODS: We conducted a retrospective multicenter cohort study on 170 patients with metastatic melanoma. The automated IHC assay was performed using the SP174 clone, and compared with results of the molecular testing. RESULTS: Evaluation of a test cohort with knowledge of the mutation status established a specific IHC pattern for the mutation. In the independent blinded analysis of the remaining cases, the anti-NRAS (Q61R) antibody accurately identified all NRAS Q61R-mutated tumors, and demonstrated 100% sensitivity and specificity. LIMITATIONS: Limitations include retrospective design and lack of multicenter interobserver reproducibility. CONCLUSION: The NRAS (Q61R) IHC assay is reliable and specific for the evaluation of the Q61R mutation status in metastatic melanoma and may be an alternative to molecular biology in evaluation of metastatic melanoma in routine practice.

Malignant Melanoma Arising in Patients with a Large Congenital Melanocytic Naevus: Retrospective Study of 10 Cases with Cytogenetic Analysis.

Large congenital melanocytic naevi (LCMN) represent the main risk factor for development of melanoma in childhood. This retrospective study of 10 cases of melanoma in patients with LCMN used fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH) (6 cases) to elucidate the clinical, histological, and cytogenetic characteristics of this rare disorder. Six melanomas were found within the LCMN, the others in lymph nodes, subcutis and brain. The LCMN was located on the trunk in 8 cases, with satellite naevi in 6 cases. Two distinct groups emerged: 5 melanomas that developed before the age of 10 years and the other after 20 years. The mortality rate was 60% and clearly correlated with clinical stage at diagnosis. Histological diagnosis was difficult in only 2 patients in whom neither immunohistochemistry nor FISH were helpful. Otherwise, CGH showed a high number of chromosomal aberrations leading to a formal diagnosis.

[Cutaneous lymphoproliferations: proposal for the use of diagnostic algorithms based on 2760 cases of cutaneous lymphoproliferations taken from the INCa networks (LYMPHOPATH and GFELC) over a two-year period]. / Lymphoproliférations cutanées : proposition d'algorithmes diagnostiques à partir de l'expérience sur 2ans des réseaux INCa (LYMPHOPATH et GFELC) sur 2760 lymphoproliférations cutanées.

INTRODUCTION: Taking as a base our retrospective study of 2760 cases of cutaneous lymphoproliferations from the LYMPHOPATH and GFELC networks, we analyzed the doubtful and discordant cases between non-expert and expert pathologists, and the interest of clinicopathological confrontation. MATERIAL AND METHODS: We defined the main diagnostic difficulties presented by cutaneous lymphoproliferations. We then designed and tested the algorithms on 20 random cases with 20 pathologists, in order to be used by any pathologist (not necessarily specialised in dermatopathology). RESULTS: The problematic differential diagnoses most frequently encountered are the following: MF or reactive dermatose; lymphoma without any other precision or reactive infiltrate; small B cell lymphoproliferation: lymphoma or reactive infiltrate; phenotyping of large B cell lymphoproliferation. We also analyzed less common problematic differential diagnoses, on the grounds that they are over- or under- diagnosed. Our test had a 72% success rate among the 20 randomly tested cases. The use of several algorithms for the same case is possible. DISCUSSION: Our study shows that an expert second-opinion is of interest in the area of cutaneous lymphoproliferations. A second opinion is useful for distinguishing a small B cell lymphoma from a HLR, and for defining a final diagnosis when the first pathologist doubts between lymphoma and reactive infiltrate. However, we demonstrate that for the problem MF or reactive dermatose, an initial clinicopathological confrontation produces more results than a second-opinion pathology review. CONCLUSION: This is the first study of cutaneous lymphoproliferations that, without excluding reactionary infiltrates, concentrates on doubtful and discordant diagnoses between non expert and expert pathologists, and which has produced tested diagnostic algorithms.