Intramolecular Cyclization and a Retro-Ene Reaction Enable the Rapid Fragmentation of a Vitamin B1-Derived Breslow Intermediate.

In solution, analogues of the Breslow intermediate formed during catalysis by benzoylformate decarboxylase (BFDC) undergo rapid, irreversible fragmentation. The ability of BFDC to prevent this reaction and preserve its cofactor is a striking example of an enzyme 'steering' a reactive intermediate towards a productive pathway. To understand how BFDC suppresses the off-pathway reactivity of this Breslow intermediate, a clear mechanistic understanding of the fragmentation reaction is required. Here, DFT calculations reveal an unexpected mechanism for the solution-phase fragmentation that involves an intramolecular cyclization and a subsequent retro-ene reaction to release the final products. Free energy profiles demonstrate that this pathway is significantly more facile than the previously proposed mechanism that invoked Breslow intermediate enolates as intermediates. Additional computations have been performed to understand why related Breslow intermediates do not undergo analogous fragmentation reactions. Calculations performed with two closely related Breslow intermediates suggest that subtle differences in the relative values of ΔG≠ for protonation and fragmentation dictate whether a given intermediate will fragment or not. These differences and the fragmentation mechanism unveiled in this work may have ramifications for the mechanism of BFDC and other thiamin-dependent enzymes and could provide general lessons related to the control of reactive intermediates by enzymes.

From Criegee to Breslow: How π-Donors Steer the Route of Olefin Ozonolysis.

While π-bonds typically undergo cycloaddition with ozone, resulting in the release of much-noticed carbonyl O-oxide Criegee intermediates, lone-pairs of electrons tend to selectively accept a single oxygen atom from O3, producing singlet dioxygen. We questioned whether the introduction of potent electron-donating groups, akin to N-heterocyclic olefins, could influence the reactivity of double bonds - shifting from cycloaddition to oxygen atom transfer or generating lesser-known, yet stabilized, donor-substituted Criegee intermediates. Consequently, we conducted a comparative computational study using density functional theory on a series of model olefins with increasing polarity due to (asymmetric) π-donor substitution. Reaction path computations indicate that highly polarized double bonds, instead of forming primary ozonides in their reaction with O3, exhibit a preference for accepting a single oxygen atom, resulting in a zwitterionic species formally identified as a carbene-carbonyl adduct. This previously unexplored reactivity potentially introduces aldehyde umpolung chemistry (Breslow intermediate) through olefin ozonolysis. Considering solvent effects implicitly reveals that increased solvent polarity further directs the trajectories toward a single oxygen atom transfer reactivity by stabilizing the zwitterionic character of the transition state. The competing modes of chemical reactivity can be explained by a bifurcation of the reaction valley in the post-transition state region.

Evaluation of Multiple Tissue Levels Frequently Upstages Patients With Clinically Localized Thin Primary Cutaneous Melanoma.

BACKGROUND: Breslow thickness (BT), ulceration, and microsatellitosis are critical prognostic parameters for cutaneous melanoma staging. These parameters can vary depending on the number of tissue levels examined from individual paraffin blocks. We sought to evaluate all prognostic histopathologic parameters in melanoma for their variations between levels, taken at regular intervals, in a single study. METHODS: We analyzed 40 consecutive cases of primary cutaneous (nonacral) melanoma through five hematoxylin and eosin sections, taken at 100 µm intervals, for staging and prognostic parameters. RESULTS: Examination of additional levels resulted in (a) an increase in BT in 47.5% (19 out of 40) of cases and (b) detection of ulceration in a further 5% (2/40). This resulted in upstaging for 20% (8 out of 40) of patients (15% because of BT, 2.5% because of ulceration, and 2.5% because of BT and ulceration). The upstaging effect was incremental, with approximately 5% of patients upstaged with each additional 100 µm interval (up to 400 µm). Incipient ulceration and epidermal consumption were infrequent (10% of cases); however, when present, ulceration was subsequently observed in half of cases. We encountered no cases where microsatellitosis was detected at deeper levels. CONCLUSION: The performance of additional tissue levels is a simple and inexpensive procedure that can improve the accuracy of staging for patients with thin (pT1) primary cutaneous melanomas. It may be pertinent for pathologists to consider additional levels for thin melanomas when a BT measurement is close to a staging threshold (e.g., within 0.1-0.3 mm for pT1a vs. pT1b, or pT1b vs. pT2a), or when incipient ulceration is encountered.

A Retrospective Study of Diameter and Breslow Thickness in Invasive Melanomas.

INTRODUCTION: A diameter larger than 6 mm is included in the criteria used in public health messages to detect a cutaneous melanoma. We aimed to investigate the independent association of Breslow thickness with the melanoma diameter. METHODS: A retrospective study was performed in patients with invasive melanomas of the nodular melanoma (NM) or superficial spreading melanoma (SSM) subtype. The quartiles of the diameter (lower, median, upper) were studied in non-parametric quantile regression model. RESULTS: In total, 537 cases of invasive melanomas were included and 60% had Breslow thickness ≤1.0 mm. There were 429 SSM (79.9%) and 108 NM (20.1%). Although NMs were significantly thicker (median Breslow thickness: 2.7 mm vs. 0.7 mm, respectively, p < 0.0001), they were not associated with larger diameter compared to SSMs (p = 0.71). After adjustment for age and sex, melanoma location and subtype, having Breslow thickness ≤1.0 mm was not significantly associated with the lower quartile, median and upper quartile of the diameter (p values: 0.063, 0.083, and 0.791, respectively). CONCLUSION: In our study including melanomas of the NM or SSM subtype, Breslow thickness was not associated with the diameter, adding evidence to support the limitations of using diameter larger than 6 mm for the detection of invasive melanomas and indicating the potential of smaller melanomas to be thicker tumors.

Breslow density ability to predict melanoma survival: should it be used in clinical practice?

BACKGROUND: Breslow density (BD) is an estimation of melanoma volume, which has emerged as a novel histopathological prognostic biomarker. OBJECTIVES: Our aim was to evaluate the role of BD as predictor of patients´ survival and assess its prognostic value in relation to overall survival (OS), disease-free survival (DFS), melanoma-specific survival (MSS) and metastasis-free survival (MFS). METHODS: A retrospective observational study in a cohort of 107 patients with invasive melanoma was conducted. Kaplan-Meier and Log-rank tests were used for 10-year survival analysis. The ability of BD and Breslow thickness (BT) to predict survival was assessed using receiver operating characteristic curves. RESULTS: The average follow-up was 115 months excluding deaths. BD ≥65% showed lower survival rates compared with the BD<65% group (log-rank test p<0.001). Area under the curve (AUC) of BD ≥65% was higher than BT's for all studied survival rates except for melanoma-specific survival, in which absolute BD showed the highest value. CONCLUSIONS: BD is proposed as a simple, valuable and inexpensive histopathological feature that could provide with valuable information to current melanoma staging, since it has proved a statistically significant prognostic value in relation to survival in melanoma patients, and comparable 10-year survival prediction ability to BT.

Efficiency of the Breslow estimator in semiparametric transformation models.

Semiparametric transformation models for failure time data consist of a parametric regression component and an unspecified cumulative baseline hazard. The nonparametric maximum likelihood estimator (NPMLE) of the cumulative baseline hazard can be summarized in terms of weights introduced into a Breslow-type estimator (Weighted Breslow). At any given time point, the weights invoke an integral over the future of the cumulative baseline hazard, which presents theoretical and computational challenges. A simpler non-MLE Breslow-type estimator (Breslow) was derived earlier from a martingale estimating equation (MEE) setting observed and expected counts of failures equal, conditional on the past history. Despite much successful theoretical and computational development, the simpler Breslow estimator continues to be commonly used as a compromise between simplicity and perceived loss of full efficiency. In this paper we derive the relative efficiency of the Breslow estimator and consider the properties of the two estimators using simulations and real data on prostate cancer survival.

Thin Amelanotic and Hypomelanotic Melanoma: Clinicopathological and Dermoscopic Features.

Background and Objectives: Amelanotic/hypomelanotic melanomas (AHMs) account for 2-8% of all cutaneous melanomas. Due to their clinical appearance and the lack of specific dermoscopic indicators, AHMs are challenging to diagnose, particularly in thinner cutaneous lesions. The aim of our study was to evaluate the clinicopathological and dermoscopic features of thin AHMs. Identifying the baseline clinical-pathological features and dermoscopic aspects of thin AHMs is crucial to better understand this entity. Materials and Methods: We divided the AHM cohort into two groups based on Breslow thickness: thin (≤1.00 mm) and thick (>1.00 mm). This stratification helped identify any significant clinicopathological differences between the groups. For dermoscopic analysis, we employed the "pattern analysis" approach, which involves a simultaneous and subjective assessment of different criteria. Results: Out of the 2.800 melanomas analyzed for Breslow thickness, 153 were identified as AHMs. Among these, 65 patients presented with thin AHMs and 88 with thick AHMs. Red hair color and phototype II were more prevalent in patients with thin AHMs. The trunk was the most common anatomic site for thin AHMs. Patients with thin AHMs showed a higher number of multiple melanomas. Dermoscopic analysis revealed no significant difference between thin AHMs and thick AHMs, except for a more frequent occurrence of residual reticulum in thin AHMs. Conclusions: Thin AHMs typically affect individuals with lower phototypes and red hair color. These aspects can be related to the higher presence of pheomelanin, which provides limited protection against sun damage. This also correlates with the fact that the trunk, a site commonly exposed to intermittent sun exposure, is the primary anatomical location for thin AHMs. Multiple primary melanomas are more common in patients with thin AHMs, likely due to an intrinsic predisposition as well as greater periodic dermatologic follow-ups in this class of patients. Apart from the presence of residual reticulum, no other significant dermoscopic differences were observed, complicating the differential diagnosis between thin and thick AHMs based on dermoscopy alone.

Clinical and Histopathologic Features of Subungual Melanoma in 57 Mexican Patients: A 5-Year Cohort Study. / Características clínicas e histopatológicas de melanoma subungueal en 57 pacientes mexicanos: una cohorte de 5 años.

Although subungual melanoma is uncommon, it is associated with worse outcomes than melanomas in other locations and accounts for 1% to 23% of all melanomas, depending on the population. The aim of this study was to describe the clinical and histopathologic features of subungual melanoma in a Mexican population. We identified 303 patients with melanoma, and of these, 19% (57 patients with a median age of 71 years) had subungual melanoma. The main sites affected were the lower limbs (52.6%) and the toe (75.4%). The most common histologic subtype was acral lentiginous melanoma (50.9%). Median Breslow thickness was 3 mm, and stage IA tumors were the most common (in 28.1% of patients). Recurrence and metastasis occurred in 19.3% and 8.8% of patients, respectively. The clinical and histopathologic features identified are similar to those described in the literature. Early diagnosis and treatment are crucial for improving prognosis.

[Translated article] Clinical and Histopathologic Features of Subungual Melanoma in 57 Mexican Patients: A 5-Year Cohort Study.

Although subungual melanoma is uncommon, it is associated with worse outcomes than melanomas in other locations and accounts for 1% to 23% of all melanomas, depending on the population. The aim of this study was to describe the clinical and histopathologic features of subungual melanoma in a Mexican population. We identified 303 patients with melanoma, and of these, 19% (57 patients with a median age of 71 years) had subungual melanoma. The main sites affected were the lower limbs (52.6%) and the toe (75.4%). The most common histologic subtype was acral lentiginous melanoma (50.9%). Median Breslow thickness was 3 mm, and stage IA tumors were the most common (in 28.1% of patients). Recurrence and metastasis occurred in 19.3% and 8.8% of patients, respectively. The clinical and histopathologic features identified are similar to those described in the literature. Early diagnosis and treatment are crucial for improving prognosis.

The importance of four-membered NHCs in stabilizing Breslow intermediates on benzoin condensation pathway.

N-heterocyclic carbenes (NHCs) have been established to be effective organocatalysts for facilitating the benzoin condensation and many other reactions. These reactions involve the formation of a Breslow intermediate (BI), which exhibits umpolung chemistry. To facilitate organocatalysis, several new cyclic carbenes are being introduced, four-membered NHCs are of special interest. Whether these NHCs can exhibit catalytic influence or not, can be evaluated by exploring the potential energy surface (PES) of the benzoin condensation reaction. Quantum chemical analysis has been carried out to compare the PES of these four-membered NHCs with that of standard five-membered NHCs to explore their catalytic ability. The barrier for the first step of the reaction for the formation of BI is comparable in all the cases. But the barrier for the second step of the reaction leading to the benzoin formation from BI is estimated to be very high for the four membered NHCs. These results indicate that the probability of identifying and isolating the BI is very high in comparison to the completion of benzoin condensation reaction in the case of the four-membered NHCs.

Risk of recurrence of nail unit melanoma after functional surgery versus amputation.

BACKGROUND: Minimally invasive nail unit melanoma (NUM) can be treated with functional surgery (FS) instead of amputation. OBJECTIVE: To determine risk factors associated with recurrence in NUM. METHODS: We retrospectively reviewed patients with NUM between 2008 and 2022 at a tertiary referral center. Multivariable Cox regression models adjusted for male sex and Breslow thickness (BT) were generated. Receiver operating characteristic analysis was performed to determine optimal cut-off points of the BT for stratifying recurrence risk. RESULTS: We evaluated 140 NUM cases (33 amputation and 107 FS). The mean BT values were 3.14 ± 2.62 mm (amputation) and 0.70 ± 1.36 mm (FS). Recurrence occurred in 10 (30.30%) patients with amputation and 23 (21.5%) with FS. Distant disease occurred in 10 (30.30%) patients with amputation and 8 (7.48%) with FS. Male sex, greater BT, amelanotic color, ulcers, and nodules were associated with greater risk for recurrence or distant disease. A BT of 0.8 mm was deemed the optimal cut-off for stratifying recurrence risk after surgery (odds ratio, 5.32; 95% CI, 2.04-13.85). LIMITATIONS: Small sample. CONCLUSION: FS can be considered for NUM with a BT < 0.8 mm, providing an amputation-sparing benefit. However, NUM with risk factors for recurrence requires patient counselling and close follow-ups.

Ultra-High Frequency Ultrasound in Melanoma Management: A New Combined Ultrasonographic-Histopathological Approach.

OBJECTIVES: The main aim of this study is to evaluate the correspondence between the ultrasonographic thickness and the Breslow thickness in melanoma using ultra-high frequency ultrasound and the intra- and inter-operator repeatability in the ultrasonographic measurements of melanoma depth. Moreover, we propose a new protocol based on a combined ultrasonographic-histopathological approach. METHODS: We analyzed 27 melanomas in a population consisted of 27 patients (mean age 57.6 years, 51.8% males), who came at the Department of Dermatology (University of Pisa, Pisa, Italy) from April 2016 to March 2018 and had an ultrasonographic examination of a suspected lesion before the surgical removal using ultra-high frequency ultrasound (Vevo®MD, Fujifilm, Visualsonics, Toronto, Canada; 70 MHz probe). B-mode images were analyzed by two skilled and blinded operators, and the maximum depth of the lesions was measured using a dedicated graphical user interface developed in Matlab R2016b (MathWorks Inc., Natick, MA), to obtain repetitive measurements. RESULTS: All melanomas appeared as band-like or oval/fusiform shaped hypoechoic inhomogeneous lesions. We observed an excellent agreement between the Breslow thickness of melanomas and the ultrasonographic thickness, as well as a reduced intra- and inter-operator variability in the ultrasonographic measurements of melanoma depth. CONCLUSIONS: We propose a ultrasonographic-histopathological protocol which may help clinicians to reduce the diagnostic delay, improve prognosis and survival rates, perform a surgical excision with negative margins, and reduce the variability in the assessment of Breslow thickness.

Consistent and robust inference in hazard probability and odds models with discrete-time survival data.

For discrete-time survival data, conditional likelihood inference in Cox's hazard odds model is theoretically desirable but exact calculation is numerical intractable with a moderate to large number of tied events. Unconditional maximum likelihood estimation over both regression coefficients and baseline hazard probabilities can be problematic with a large number of time intervals. We develop new methods and theory using numerically simple estimating functions, along with model-based and model-robust variance estimation, in hazard probability and odds models. For the probability hazard model, we derive as a consistent estimator the Breslow-Peto estimator, previously known as an approximation to the conditional likelihood estimator in the hazard odds model. For the hazard odds model, we propose a weighted Mantel-Haenszel estimator, which satisfies conditional unbiasedness given the numbers of events in addition to the risk sets and covariates, similarly to the conditional likelihood estimator. Our methods are expected to perform satisfactorily in a broad range of settings, with small or large numbers of tied events corresponding to a large or small number of time intervals. The methods are implemented in the R package dSurvival.

Invasive Cutaneous Melanoma: Evaluating the Prognostic Significance of Some Parameters Associated with Lymph Node Metastases.

Background and Objectives: This study aimed to assess the clinical-pathological profile of patients with invasive cutaneous melanomas and to identify the parameters with a prognostic role in the lymph nodal spread of this malignant tumor. Materials and Methods: We performed a retrospective study on patients with invasive cutaneous melanomas who underwent surgery in the "Pius Brînzeu" County Clinical Emergency Hospital from Timișoara, Romania, and were evaluated for the status of loco-regional lymph nodes. We selected and analyzed some parameters searching for their relationship with lymph node metastases. Results: We identified 79 patients with invasive cutaneous melanomas (29 men and 50 women, mean age 59.36 years). A percentage of 58.3% of melanomas had Breslow tumor thickness >2 mm; 69.6% of melanomas showed a Clark level IV-V. Tumor ulceration was present in 59.5% of melanomas. A mitotic rate of ≥5 mitoses/mm2 was observed in 48.1% of melanomas. Tumor-infiltrating lymphocytes (TILs), non-brisk, were present in 59.5% of cases and 22.8% of patients had satellite/in-transit metastasis (SINTM). Tumor regression was identified in 44.3% of cases. Lymph nodes metastases were found in 43.1% of patients. Statistical analysis showed that lymph node metastases were more frequent in melanomas with Breslow thickness >2 mm (p = 0.0002), high Clark level (p = 0.0026), mitotic rate >5 mitoses/mm2 (p = 0.0044), ulceration (p = 0.0107), lymphovascular invasion (p = 0.0182), SINTM (p = 0.0302), and non-brisk TILs (p = 0.0302). Conclusions: The Breslow thickness >2 mm, high Clark level, high mitotic rate and ulceration are the most important prognostic factors for lymph nodal spread in cutaneous melanomas. However, some melanomas without these clinical-pathological features can have an unexpected, aggressive evolution, which entails the necessity of close and prolonged clinical follow-up of patients, including those with lesions considered without risk.

Primary Melanoma Histopathologic Predictors of Sentinel Lymph Node Positivity: A Proposed Scoring System for Risk Assessment and Patient Selection in a Clinical Setting.

Background and Objectives: The careful selection of adequate SLNB candidates not only aims at reducing the surgical risk while identifying SLN metastasis, but also plays a crucial role in identifying the patients eligible for adjuvant therapy. Objectives: The purpose of our study was to investigate the clinical and histologic aspects of primary melanomas that correlate with the likelihood of a positive SLNB result. Materials and Methods: A total of 101 primary melanoma patients who underwent sentinel lymph node biopsies were included in the study. General patient demographics were obtained as well as localization and melanoma-specific characteristics of primary melanoma from histologic reports in addition to data derived from SLNB melanoma histopathology reports. Results: The patients with positive SLN results had a statistically significant increased Breslow thickness (3.8 mm vs. 1.97 mm, p = 0.002), higher mitotic index rate (5/mm2 vs. 2/mm2, p = 0.009), as well as the presence of ulceration (68.4% vs. 31.6%, p = 0.007). Univariate regression analysis showed the Breslow thickness (p = 0.008), the mitotic index rate (p = 0.054), the presence of ulceration (p = 0.009), as well as the pT3-4 stage (p = 0.009) to be significant predictors of SLN positivity. The optimal cut-off values for Breslow thickness and the number of mitoses scores were determined based on ROC curve analysis. Using the Breslow thickness, mitotic index rate, presence of ulceration, and pT3-4 stage significant coefficients from the univariate regression model, a chance prediction score was developed. Conclusions: The newly developed and proposed scoring system can aid in patient selection for SLN biopsy by facilitating a more efficient risk assessment in the detection of lymph node metastases in melanoma patients.

A Masked Form of an O-Borylated Breslow Intermediate for the Diastereoselective FLP-Type Activation of Aldehydes.

Breslow intermediates are very often elusive species whose application in frustrated Lewis pair (FLP) chemistry is unprecedented. Described herein is the use of a masked form of an O-borylated Breslow (OBB) intermediate that performs FLP-type activation of the carbonyl function of five different benzaldehyde derivatives with complete diastereoselectivity. The resulting compounds are characterised in solution by NMR spectroscopy (compounds 4-8) and in solid state by X-ray diffraction analysis (compounds 4-6). A combined kinetic and theoretical investigation reveals the associative nature of the rate determining step and suggests that the OBB intermediate part is never released during the whole process.

The progressive relationship between increasing Breslow thickness and decreasing survival is lost in patients with ultrathick melanomas (≥15 mm in thickness).

BACKGROUND: Survival tends to decrease as the Breslow thickness of a primary melanoma increases. However, little is known about the prognostic value of Breslow thickness in patients with very thick melanomas. OBJECTIVE: We sought to assess survival in patients with melanomas ≥4.0 mm in Breslow thickness. METHODS: A pooled cohort of 5595 patients (4107 Dutch and 1488 Australian) with melanomas ≥4.0 mm in thickness diagnosed from 2000 to 2014 was analyzed. Standard and spline Cox regressions were generated for overall survival (OS) and recurrence-free survival (RFS). RESULTS: The median follow-up was 3.4 years. The continuous hazard ratios (HRs) for OS and RFS increased steadily as the Breslow thickness increased to 15 mm, stabilized up to 20 mm, and decreased thereafter. Using patients with melanomas 4 to <10 mm thick as a reference group, the categoric HR for OS increased up to the 15- to -<20-mm thickness category and then decreased (HR, 1.46 [95% CI, 1.29-1.66], P < .0001 for 10-<15 mm; HR, 1.97 [95% CI, 1.55-2.51], P < .0001 for 15-<20 mm; and HR, 1.36 [95% CI, 1.07-1.84], P = .045 for ≥20 mm). For the RFS, similar trends were observed. LIMITATIONS: Retrospective study. Small cohorts of patients with melanomas 15-<20mm and ≥20mm. CONCLUSION: The progressive relationship between increasing Breslow thickness and decreasing survival is lost in patients with melanomas ≥15 mm in thickness.

Preoperative Ultrasound-Guided Incisional Biopsy Enhances the Pathological Accuracy of Incisional Biopsy of Cutaneous Melanoma: A Prospective Clinical Trial in Chinese Patients.

OBJECTIVES: To assess the feasibility of preoperative ultrasound (US)-guided incisional biopsy through a prospective controlled clinical trial. METHODS: This was a prospective, double-arm, single-center study of Chinese patients. Thirty patients were enrolled in the study. Fourteen patients received incisional biopsies for which the choice of biopsy area relied on a clinical evaluation, and 16 patients received incisional biopsies for which the choice of biopsy area relied on a US-guided evaluation. The following procedure was used in the US-guided incisional biopsy group: 1) clinical and dermoscopic evaluation of skin lesions; 2) US examination; 3) incisional biopsy; 4) surgical excision; and 5) histopathological examination. The same procedure was used in the non-US-guided group except without US examination. RESULTS: In the non-US-guided group, the mean tumor thicknesses obtained from incisional biopsy and postoperative histopathological examination were 2.1 and 4.1 mm, respectively. Seven melanomas were underestimated by incisional biopsy, resulting in margins narrower than currently recommended. In the US-guided group, the mean tumor thicknesses obtained from US, incisional biopsy, and postoperative histopathological examination were 3.4, 2.9, and 2.7 mm, respectively. In only 3 melanomas was the tumor thickness of the incisional biopsy less than that of the postoperative histopathological examination, demonstrating that US-guided biopsy obtains the maximum thickness area. CONCLUSIONS: Preoperative US-guided incisional biopsy can enhance the pathological accuracy of incisional biopsy, which may allow us to better perform surgical excision with safe peripheral surgical margins.

Malignant Melanoma in Lagos, Nigeria: Elucidating Histopathologic Prognostic Factors.

BACKGROUND: Malignant melanoma (MM) is the most lethal of all cutaneous malignancies, accounting for about 79% of skin cancer related deaths. In blacks, it is associated with greater morbidity and mortality compared to Caucasians. Breslow thickness and ulceration status are two of the most important histopathologic prognostic factors in MM. No study on MM in Nigeria has however examined these factors. METHODS: Formalin-fixed paraffin-embedded (FFPE) tissue blocks and corresponding Haematoxylin and Eosin (H&E) stained slides of all confirmed cases of MM from January 2005 to December 2014 in the AMP Department of Lagos University Teaching Hospital (LUTH) were retrieved. RESULTS: Fifty-two MM cases were histologically diagnosed in LUTH during the study period which represented 1.0% of total solid malignancies. Forty-three of these occurred in the skin accounting for 19.7% of all skin malignancies and making MM the 3rd commonest skin malignancy after squamous cell carcinoma (SCC) and kaposi sarcoma (KS). Eighty eight percent (88%) of the tumour were in Clark's stage IV and V while 84% had Breslow thickness >4mm. Ulceration was present in 67%. The Clark's level and Breslow thickness were correlated with the ulceration status of the tumour. There is significant correlation between the Breslow thickness and ulceration with p-value < 0.05 while there is no significant association between the Clark's level and ulceration. CONCLUSION: MM constituted a significant proportion of skin malignancy in LUTH and majority of the cases present at an advanced stage. Breslow thickness and ulceration statuses of the tumour are important histopathologic parameters that should be reported in all MM biopsies.

CONTEXTE: Le mélanome malin (MM) est la plus meurtrière de toutes les affections malignes cutanées, représentant environ 79 % des décès liés au cancer de la peau. Chez les Noirs, il est associé à une plus grande morbidité et de mortalité plus élevées que chez les Caucasiens. L'épaisseur de Breslow et le statut d'ulcération sont deux des facteurs pronostiques histopathologiques les plus importants du MM. Aucune étude sur le MM au Nigeria n'a cependant examiné ces facteurs. MÉTHODES: Nous avons récupéré des blocs de tissus fixés au formol et incorporés en paraffine (FFPE) ainsi que les lames correspondantes colorées à l'hématoxyline et à l'éosine (H&E) de tous les cas confirmés de MM entre janvier 2005 et décembre 2014 dans le département AMP du Lagos University Teaching Hospital (LUTH). RÉSULTATS: Cinquante-deux cas de MM ont été diagnostiqués histologiquement au LUTH pendant la période d'étude, ce qui représente 1,0 % du total des tumeurs malignes solides. Quarantetrois de ces cas sont survenus dans la peau, ce qui représente 19,7% de toutes les tumeurs cutanées et fait du MM la troisième tumeur cutanée la plus fréquente après le carcinome épidermoïde (SCC) et le sarcome de Kaposi (KS). Quatre-vingt huit pour cent (88%) de la tumeur étaient au stade IV et V de Clark tandis que 84% avaient une épaisseur de Breslow e"4mm. Une ulcération était présente dans 67% des cas. Le niveau de Clark et l'épaisseur de Breslow étaient corrélés avec le statut d'ulcération de la tumeur. Il existe une corrélation significative entre l'épaisseur de Breslow et l'ulcération avec une valeur p < 0,05 alors qu'il n'y a pas d'association significative entre le niveau de Clark et l'ulcération. CONCLUSION: Le MM constitue une proportion significative des tumeurs cutanées malignes à l'hôpital LUTH et la majorité des cas sont à un stade avancé. L'épaisseur de Breslow et les statuts d'ulcération de la tumeur sont des paramètres histopathologiques importants qui devraient être rapportés dans toutes les biopsies de MM. Mots clés: Mélanome malin, épaisseur de Breslow, niveau de Clark, ulcération, facteurs pronostiques.

Formation of Breslow Intermediates from N-Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal.

Under aprotic conditions, the stoichiometric reaction of N-heterocyclic carbenes (NHCs) such as imidazolidin-2-ylidenes with aldehydes affords Breslow Intermediates (BIs), involving a formal 1,2-C-to-O proton shift. We herein report kinetic studies (NMR), complemented by DFT calculations, on the mechanism of this kinetically disfavored H-translocation. Variable time normalization analysis (VTNA) revealed that the kinetic orders of the reactants vary for different NHC-to-aldehyde ratios, indicating different and ratio-dependent mechanistic regimes. We propose that for high NHC-to-aldehyde ratios, the H-shift takes place in the primary, zwitterionic NHC-aldehyde adduct. With excess aldehyde, the zwitterion is in equilibrium with a hemiacetal, in which the H-shift occurs. In both regimes, the critical H-shift is auto-catalyzed by the BI. Kinetic isotope effects observed for R-CDO are in line with our proposal. Furthermore, we detected an H-bonded complex of the BI with excess NHC (NMR).