Photodynamic therapy (PDT) is a multimodality cancer treatment available for the palliation or eradication of systemic and cutaneous malignancies. In this thesis, the application of PDT is for the treatment of non-melanoma skin cancer (NMSC). While PDT has a well-documented track record, there are, at this time no significant indicators to suggest the superiority of one treatment regime over the next. The motivation for this work is to provide additional evidence pertaining to PDT treatment variables, and to assist in optimising PDT treatment regimes. One such variable is the treatment light dose. Determining the light dose more accurately would assist in optimising treatment schedules. Furthermore, choice of photosensitiser pro-drug type and application times still lack an evidence base. To address issues concerning treatment parameters, fluorescence spectroscopy – a valuable optical diagnostic technique – was used. Monitoring the in vivo PpIX fluorescence and photobleaching during PDT was employed to provide information pertaining to the progression of treatment. This was demonstrated by performing a clinical study at the Photobiology Unit, Ninewells Hospital and Medical School, Dundee. Two different photosensitiser pro-drugs – either 5-aminolaevulinic acid (ALA) or its methyl ester (MAL) – were investigated and based on the fluorescence and pain data recorded both may be equally suitable for topical PDT. During PDT, surface fluorescence is observed to diminish with time – due to photobleaching – although cancerous cells may continue to be destroyed deep down in the tissue. Therefore, it is difficult to ascertain what is happening at depth in the tumour. This raised the questions; How long after surface PpIX fluorescence has diminished is the PDT treatment still effective and to what depths below the surface is effective treatment provided? In order to address these important questions, a three-dimensional (3D) Monte Carlo radiation transfer (MCRT) model was used to compute the light dose and the ¹O₂ production within a tumour, and the PpIX fluorescence emission from the tumour. An implicit dosimetry approach based on a single parameter – fluorescence photobleaching – was used in order to determine the ¹O₂ generation, which is assumed to be related to tissue damage. Findings from our model recommended administering a larger treatment light dose, advocating an increase in the treatment time after surface PpIX fluorescence has diminished. This increase may ultimately assist in optimising PDT treatment regimes, particularly at depth within tumours.

O trabalho apresentado foi realizado em duas etapas independentes e baseou-se no estudo de diferentes sistemas nanométricos para viabilizar a aplicação da ftalocianina de cloro alumínio (ClAlPc) na terapia fotodinâmica (TFD) para o tratamento do câncer de pele do tipo melanoma. O fármaco fotossensibilizante (FS) utilizado apresenta propriedades físico-químicas que lhe permitem exercer sua atividade fotodinâmica com excelência, sem a interferência do cromóforo endógeno melanina existente nas células melanocíticas. Para driblar sua elevada hidrofobicidade, ClAlPc foi encapsulada em sistemas nanométricos para administração em meio fisiológico. Inicialmente nanopartículas lipídicas sólidas (NLS) foram desenvolvidas por emulsificação direta, após um estudo de elaboração do diagrama de fases. O compritol foi o lipídio sólido escolhido para compor as NLS, com diferentes concentrações de ClAlPc. Todas as formulações desenvolvidas foram devidamente caracterizadas, com tamanho médio entre 100 e 200 nm, baixa polidispersão, potencial zeta adequadamente negativo (~|30| mV), drug loading de ClAlPc entre 76-94% (com pequena redução após 24 meses) e alta eficiência de encapsulação (E.E.). A morfologia arredondada das nanopartículas foi confirmada por microscopia eletrônica de transmissão e de força atômica. A estabilidade das NLS foi de 24 meses. A avaliação da cristalinidade do lipídio revelou a integração da ClAlPc à matriz lipídica da NLS, presença de estruturas polimórficas e grau de cristalinidade adequado, sem alterações após 24 meses. Nos estudos de difusão in vitro, observou-se que ftalocianina encapsulada nas NLS acumulam-se preferencialmente na epiderme e derme do que no estrato córneo, sem traços de permeação do ativo. Foi confirmado o caráter biocompatível das NLS sobre fibroblastos NIH-3T3. A ftalocianina encapsulada nas NLS não foi tóxica na linhagem de melanoma B16-F10 na ausência de luz, porém, apresentou excelente efeito fototóxico (0,75 ?g mL-1 de ClAlPc nanoencapsulada e irradiação entre 0,5 e 2,0 J cm-2), com redução da viabilidade celular de 87%. O segundo sistema de veiculação estudado foram as vesículas cataniônicas (VesCat), que se formam espontaneamente em água com o tensoativo TriCat 12. A obtenção das vesículas contendo ClAlPc envolve uma etapa adicional, para remoção de solvente orgânico, que foi aprimorada, reduzindo o tempo de produção em 55%. As VesCat/ClAlPc obtidas mantiveram suas propriedades físico-químicas e morfologia arredondada (confirmada por microscopia eletrônica de varredura), drug loading de 47% e alta E.E. Os resultados comprovaram que a aplicação desses dois sistemas nanométricos é altamente eficiente para aplicação da TFD no tratamento do câncer de pele do tipo melanoma ou outras doenças cutâneas, apresentando características favoráveis para avanços nos estudos de fase clínica e pré-clínica. / The present work was conducted in two independent steps, which were based on the study of different nanometric systems that make feasible the application of aluminum phthalocyanine chloride (ClAlPc) in the photodynamic therapy (PDT) to the melanoma skin cancer treatment. The photosensitizer (PS) used has physical-chemical properties that allow it to perform its photodynamic activity with excellence, without the interference of the melanin, an endogenous chromophore found in melanotic cells. In order to circumvent the high PS hydrophobicity, ClAlPc was encapsulated into nanosystems to administration in physiological environment. At first, solid lipid nanoparticles (SLN) were developed by direct emulsification process after drawing up phase diagram study. The solid lipid compritol was chosen to make the SLN, produced with different ClAlPc concentrations. The developed samples were properly characterized with mean size between 100-200 nm, low polydispersity, negative zeta potential (~|30| mV), ClAlPc drug loading around 76-94% (with slight decrease after 24 months) and high encapsulation efficiency (EE). The round shape of SLN was confirmed by transmission electron microscopy and atomic force microscopy. The nanoparticles were stable for at least 24 months. The evaluation of lipid crystallinity has proved the ClAlPc integration to SLN lipid matrix, the presence of polymorphic structures and a suitable crystalline degree, without large variations after 24 months. In the in vitro diffusion studies were observed that phthalocyanine conveyed in the nanoparticles accumulates preferably in the epidermis and dermis than in the stratum corneum, without any drug permeation traits. The NLS biocompatibility was confirmed on NIH-3T3 fibroblasts. ClAlPc-loaded NLS did not exhibit toxicity on B16-F10 melanoma cell line in the dark, but it was shown their outstanding phototoxicity effect (0.75 ?g mL-1 of encapsulated ClAlPc and irradiation between 0.5 and 2.0 J cm-2) with cell viability reduction of 87%. The second drug delivery system studied were the catanionic vesicles (VesCat) that are spontaneously obtained by mixing the self-assembly surfactant TriCat 12 in water. The production of ClAlPc-loaded vesicles comprises an additional step (to remove the organic solvent) that was optimized, saving 55% of the production time. The final VesCat/ClAlPc kept their physical-chemical properties and round shape (confirmed by scanning electron microscopy), drug loading of 47% and high EE. Hence, the results have proved the great efficiency of these two nanometric systems applied in the PDT to the treatment of melanoma skin cancer and other cutaneous disease, useful features for further progress towards preclinical and clinical trials.

Genetic changes are hallmarks of cancer development involving the activation and/or inactivation of oncogenes and tumour suppressor genes, respectively. In non-melanoma skin cancer (NMSC) development, the initiation of genetic mutations results from exposure to solar ultraviolet radiation. Non-melanoma skin cancers are comprised of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Several related cutaneous lesions also exist, of which solar keratoses (SK) are widely accepted as a precursor dysplasia to SCC development. The study of recurrent genetic changes present within NMSC and SK should help reveal causative mutations in skin cancer development. Such analysis could also elucidate links in the genetic similarity of these dysplasia. The rapid screening of numerical changes in DNA sequence copy number throughout the entire genome has been made possible by the advent of comparative genomic hybridisation (CGH). This technique enables the identification of net gains and loss of genetic material within a tumour DNA sample. Chromosomal regions of recurrent gain or loss identify loci containing putative oncogenes and tumour suppressor genes, respectively with potential roles in NMSC tumourigenesis. Used in conjunction with tissue microdissection and universal degenerate PCR techniques this can enable the elucidation of aberrations in small histologically distinct regions of tumour. Such a technique can utilize archival material such as paraffin embedded tissue, which is the major source of neoplastic material available for cancer research. This study used the CGH technique to investigate aberrations in BCC, SCC and SK samples. The screening of copy number abnormalities (CNAs) in BCC revealed that although these tumours were close to diploid and generally genetically stable, they did contain several recurrent aberrations. The loss of genetic material at 9q was identified in a third of BCC tumours studied. This is characteristic of inactivation of the PTCH tumour suppressor gene, a known attribute in some sporadic BCC development. Validation of this loss was performed via loss of heterozygosity, demonstrating good concordance with the CGH data. In addition the over-representation of the 6p chromosome arm was revealed in 47% of biopsies. This novel CNA is also commonly observed in other cutaneous neoplasias, including Merkel cell carcinoma and malignant melanoma. This suggests a possible common mechanism in development and or promotion in these cutaneous dysplasias, the mechanisms of which have yet to be clearly defined. In contrast to BCC, numerical genetic aberrations in SCC and SK were much more frequent. Several regions of recurrent gain were commonly shared between both dysplasias including gain of 3q, 4p, 5p, 8q, 9q, 14q, 17p, 17q and 20q. Common chromosomal regions of loss included 3p, 8p, 9p, 11p, 13q and 17p. In addition loss of chromosome 18 was significantly observed in SCC in comparison to SK, a possible defining event in SK progression to SCC. The identification of shared genetic aberrations suggests a clonal and genetic relationship between the two lesions. This information further supports the notion for re-classification of SK to an SCC in situ or superficial SCC. Finally, the CNAs detected have been similarly observed in other squamous cell-derived tumours, for example cervical and head and neck SCC. This provides further evidence to common mechanisms involved in the initiation, development and progression of SCC neoplasia. This study has identified a number of recurrent chromosomal regions, some of which are novel in NMSC development. The further delineation of these loci should provide additional evidence of their significance and degree of involvement in NMSC tumourigenesis. The identification of the cancer-causing genes mapped to these loci will further demarcate the genetic mechanisms of BCC and SCC progression. An understanding of the events involved in skin cancer formation and progression should shed additional light on molecular targets for diagnostics, management and therapeutic treatment.

A previous population-based study of survival in Chronic Lymphocytic Leukemia (CLL) patients in the province of Manitoba demonstrated a lower five-year relative survival among CLL patients compared with the age- and gender-adjusted general population. This decreased relative survival was most pronounced among elderly male CLL patients. In this study, we have demonstrated that the reduced five-year relative survival observed in CLL patients compared to the general population of Manitoba may partially be attributed to increased risk of second cancers and non-referral to specialized CLL clinics. The increased risk of second cancers in CLL patients compared to Follicular Lymphoma (FL), a similar indolent B cell malignancy, was only observed after CLL diagnosis indicating that a CLL-specific factor may be responsible for the increased risk of second cancers in these patients. The risk of second cancers is independent of treatment and surveillance bias but is further increased with chemotherapy. A superior outcome in CLL patients who have been referred to the CancerCare Manitoba (CCMB) specialized CLL clinic was observed that was independent of age, gender, treatment and history of previous cancers. This superior outcome was most pronounced in the elderly CLL patients. We propose that CLL patients should be referred to CLL-specific hematologists and, where not possible, that guidelines created by such experts be followed. Appropriate screening for second cancers should be performed during routine follow up of CLL patients.

O trabalho apresentado foi realizado em duas etapas independentes e baseou-se no estudo de diferentes sistemas nanométricos para viabilizar a aplicação da ftalocianina de cloro alumínio (ClAlPc) na terapia fotodinâmica (TFD) para o tratamento do câncer de pele do tipo melanoma. O fármaco fotossensibilizante (FS) utilizado apresenta propriedades físico-químicas que lhe permitem exercer sua atividade fotodinâmica com excelência, sem a interferência do cromóforo endógeno melanina existente nas células melanocíticas. Para driblar sua elevada hidrofobicidade, ClAlPc foi encapsulada em sistemas nanométricos para administração em meio fisiológico. Inicialmente nanopartículas lipídicas sólidas (NLS) foram desenvolvidas por emulsificação direta, após um estudo de elaboração do diagrama de fases. O compritol foi o lipídio sólido escolhido para compor as NLS, com diferentes concentrações de ClAlPc. Todas as formulações desenvolvidas foram devidamente caracterizadas, com tamanho médio entre 100 e 200 nm, baixa polidispersão, potencial zeta adequadamente negativo (~|30| mV), drug loading de ClAlPc entre 76-94% (com pequena redução após 24 meses) e alta eficiência de encapsulação (E.E.). A morfologia arredondada das nanopartículas foi confirmada por microscopia eletrônica de transmissão e de força atômica. A estabilidade das NLS foi de 24 meses. A avaliação da cristalinidade do lipídio revelou a integração da ClAlPc à matriz lipídica da NLS, presença de estruturas polimórficas e grau de cristalinidade adequado, sem alterações após 24 meses. Nos estudos de difusão in vitro, observou-se que ftalocianina encapsulada nas NLS acumulam-se preferencialmente na epiderme e derme do que no estrato córneo, sem traços de permeação do ativo. Foi confirmado o caráter biocompatível das NLS sobre fibroblastos NIH-3T3. A ftalocianina encapsulada nas NLS não foi tóxica na linhagem de melanoma B16-F10 na ausência de luz, porém, apresentou excelente efeito fototóxico (0,75 ?g mL-1 de ClAlPc nanoencapsulada e irradiação entre 0,5 e 2,0 J cm-2), com redução da viabilidade celular de 87%. O segundo sistema de veiculação estudado foram as vesículas cataniônicas (VesCat), que se formam espontaneamente em água com o tensoativo TriCat 12. A obtenção das vesículas contendo ClAlPc envolve uma etapa adicional, para remoção de solvente orgânico, que foi aprimorada, reduzindo o tempo de produção em 55%. As VesCat/ClAlPc obtidas mantiveram suas propriedades físico-químicas e morfologia arredondada (confirmada por microscopia eletrônica de varredura), drug loading de 47% e alta E.E. Os resultados comprovaram que a aplicação desses dois sistemas nanométricos é altamente eficiente para aplicação da TFD no tratamento do câncer de pele do tipo melanoma ou outras doenças cutâneas, apresentando características favoráveis para avanços nos estudos de fase clínica e pré-clínica. / The present work was conducted in two independent steps, which were based on the study of different nanometric systems that make feasible the application of aluminum phthalocyanine chloride (ClAlPc) in the photodynamic therapy (PDT) to the melanoma skin cancer treatment. The photosensitizer (PS) used has physical-chemical properties that allow it to perform its photodynamic activity with excellence, without the interference of the melanin, an endogenous chromophore found in melanotic cells. In order to circumvent the high PS hydrophobicity, ClAlPc was encapsulated into nanosystems to administration in physiological environment. At first, solid lipid nanoparticles (SLN) were developed by direct emulsification process after drawing up phase diagram study. The solid lipid compritol was chosen to make the SLN, produced with different ClAlPc concentrations. The developed samples were properly characterized with mean size between 100-200 nm, low polydispersity, negative zeta potential (~|30| mV), ClAlPc drug loading around 76-94% (with slight decrease after 24 months) and high encapsulation efficiency (EE). The round shape of SLN was confirmed by transmission electron microscopy and atomic force microscopy. The nanoparticles were stable for at least 24 months. The evaluation of lipid crystallinity has proved the ClAlPc integration to SLN lipid matrix, the presence of polymorphic structures and a suitable crystalline degree, without large variations after 24 months. In the in vitro diffusion studies were observed that phthalocyanine conveyed in the nanoparticles accumulates preferably in the epidermis and dermis than in the stratum corneum, without any drug permeation traits. The NLS biocompatibility was confirmed on NIH-3T3 fibroblasts. ClAlPc-loaded NLS did not exhibit toxicity on B16-F10 melanoma cell line in the dark, but it was shown their outstanding phototoxicity effect (0.75 ?g mL-1 of encapsulated ClAlPc and irradiation between 0.5 and 2.0 J cm-2) with cell viability reduction of 87%. The second drug delivery system studied were the catanionic vesicles (VesCat) that are spontaneously obtained by mixing the self-assembly surfactant TriCat 12 in water. The production of ClAlPc-loaded vesicles comprises an additional step (to remove the organic solvent) that was optimized, saving 55% of the production time. The final VesCat/ClAlPc kept their physical-chemical properties and round shape (confirmed by scanning electron microscopy), drug loading of 47% and high EE. Hence, the results have proved the great efficiency of these two nanometric systems applied in the PDT to the treatment of melanoma skin cancer and other cutaneous disease, useful features for further progress towards preclinical and clinical trials.

No description available.

No description available.

No description available.

In den letzen Jahren gab es durch epidemiologische und molekularbiologische Studien vermehrt Hinweise, dass kutane humane Papillomviren (HPV) ursächlich an der Entstehung nicht-melanozytärer Hauttumore (engl. NMSC) beteiligt sind. Ziel der vorliegenden Arbeit war die Identifizierung molekularer Mechanismen der viralen Proteine E6 und E7 kutaner HPV-Typen. Die E6 oder E7 Gene der verschiedenen HPV-Typen 1, 4, 5, 8, 20, 38 und RTRX7 wurden untersucht. Natürliche Wirtszellen dieser Viren, humane primäre Keratinozyten (HPK) der Haut, wurden mit rekombinanten, für E6 oder E7 kodierenden Retroviren infiziert. Die Analysen erfolgten in Monolayer-Kultur (undifferenzierte Keratinozyten) oder in organotypischen Hautmodellen (Induktion der Keratinozytendifferenzierung). Die Expression von E6 oder E7 führte in Monolayer-HPK zu einer Verlängerung der Lebensspanne und zu einer deutlich erhöhten Verdoppelungsrate. Eine Telomeraseaktivierung, die charakteristisch für immortale Zellen ist, wurde nur in HPV 8 E6 positiven HPK nachgewiesen. In organotypischen Hautmodellen induzierte das E7 Protein von HPV 1, 4 und 38 starke Veränderungen in der Differenzierung sowie eine Zunahme der Proliferation. Weiterhin wurde eine Aufhebung der normalen Zellzykluskontrolle in suprabasalen HPV 5 E7 oder HPV 8 E7 beobachtet. Hinweise auf ein starkes invasives Potential von E7-infizierten HPK wurden für HPV 8 E7 bestätigt und für HPV 4 E7, HPV 38 E7 und RTRX7 E7 erweitert. Molekulare Mechanismen der viralen Gene E6 und E7 kutaner HPV unterscheiden sich von mukosalen Typen. Das Mehrstufenmodell der Karzinogenese beinhaltet eine Reihe fundamentaler Zelltransformationen, die für eine Tumorgenese nötig sind. In dieser Arbeit beschriebene Mechanismen der Modulation der Zelldifferenzierung und Zellproliferation durch die kutanen HPV-Typen 4, 5, 8 und 38 können unter Umständen zur Induktion und Progression früher Stadien von Plattenepithelkarzinomen (SCC) beitragen. / In the last years epidemiologic and molecular biological studies accumulated increasing evidence that cutaneous human papillomaviruses are etiologically involved in the formation of non-melanoma skin cancer (NMSC). The presented work aims to identify the underlying molecular mechanisms of the viral proteins E6 and E7 of cutaneous HPV types. The E6 and E7 genes of the different HPV types 1, 4, 5, 8, 20, and RTRX7, which are in vivo associated with cutaneous benign or malignant lesions, were studied. Natural host cells of these viruses, human primary keratinocyts (HPK) of the skin, were infected with recombinant E6 and E7 encoding retroviruses. The following analyses were performed in monolayer culture (non-differentiated keratinocytes) or in organotypic skin culture (induction of keratinocyte differentiation). The expression of E6 and E7 elongated the life span of monolayer HPK and significantly increased the doubling rate. An activation of the telomerase, characteristic for immortalized cells, was only detected in HPV 8 E6 positive cells. In organotypic skin cultures E7 of HPV 1, 4 and 38 induced drastic changes in differentiation and proliferation. Additionally an impairment of the normal cell cycle control in suprabasale HPV 5 E7 and 8 E7 cultures was seen. Hints for a strong invasive potential of E7 infected HPK were proven for HPV 8 E7 and expanded to HPV 4 E7, HPV 38 E7 and RTRX E7. The viral E6 and E7 genes of cutaneous and mucosal HPV types exhibit different molecular mechanisms. The multistep model of carcinogenesis includes a series of fundamental cell transformations necessary for tumorigenesis. Mechanisms for the modulation of cell differentiation and proliferation by cutaneous HPV types 4, 5, 8 and 38 described in this work could potentially contribute to the induction and progression of early stages of squamous cell carcinoma.

Background. The development of non-invasive imaging techniques has been stimulated by the shortcomings of histopathology. Currently the only valid diagnostic technique in dermatology is skin biopsy which remains a painful, invasive intervention for the patient. Moreover, this approach is not always convenient for monitoring and follow-up of a skin disease. Optical imaging technologies could solve these shortcomings as they are fast, precise, repeatable and painless. There are four established non-invasive skin imaging techniques used in daily practice: dermoscopy, high-frequency ultrasound, reflectance confocal microscopy (RCM) and conventional optical coherence tomography (C-OCT). In imaging there is a trade-off between resolution and penetration depth. The former permits the visualization of cells, if the resolution is at least 3 µm. The latter enables the recognition of patterns and structures in deeper layers of the skin if the penetration depth is deeper than 150 µm. New non-invasive techniques using infrared light sources have been developed recently. The technique used in this work is a high-definition optical coherence tomography (HD-OCT).Objectives. The overall aims of this thesis were the feasibility of HD-OCT to visualize in/ex vivo, in real time and in 3-D the cellular and structural morphology of the skin, secondly the assessment of the capability of this technology to measure in vivo and real time the cutaneous optical properties, and finally the determination of the contribution of this technique to the non-invasive near-infrared imaging technologies. Five specific objectives have been established: i) could cells be observed in their 3-D microenvironment in normal and diseased skin, ii) could we describe morphologic features of cells and structures in normal and diseased skin (m_HD-OCT), iii) could these morphologic features be quantified by optical property analysis (o_HD-OCT), iv) was it possible to perform accurate thickness measurements in normal and diseased skin, and finally v) what was the diagnostic potential of this technique?Methodology. HD-OCT uses a combination of parallel time-domain interferometry, high power tungsten lamp (with Gaussian filter, very low lateral coherence and ultra-high bandwidth (1300 nm +/- 100 nm)), and last but not least, full field illumination with real time focus tracking. A constant homogeneous resolution of 3 µm resolution in all three dimensions is obtained up to a depth of 570 µm. Hence, the system is capable of capturing real time full 3-D images. Moreover, the in vivo assessment of optical properties of the skin is only applicable to OCT when operating in focus-tracking mode, which is the case for HD-OCT. The means to obtain answers to the five specific questions were the comparison of en face HD-OCT images with RCM and HD-OCT cross-sectional images with histopathology and C-OCT. Results. At least 160 line pares were observed by imaging a high resolution phantom with HD-OCT. This suggested a 3 µm lateral resolution. The presence of cells such as keratinocytes, melanocytes, inflammatory cells, fibroblasts and melanophages in their 3-D cutaneous microenvironment in vivo as well as ex vivo has been demonstrated .A qualitative description of structures and patterns in normal and diseased skin could be performed by HD-OCT. Clear structural changes of the epidermis, dermo-epidermal junction, papillary dermis and reticular dermis related to intrinsic skin ageing could be observed. Lobulated structures, surrounded by stretched stromal fibers and arborizing vessels, could be demonstrated in nodular basal cell carcinoma (BCC). The o_HD-OCT of normal and diseased skin could be assessed in vivo. This approach permitted the quantitative assessment of the OCT signal attenuation profiles of normal healthy skin, actinic keratosis (AK) and squamous cell carcinoma (SCC). Differences in signal attenuation profiles could be demonstrated between these three groups. These differences were also observed between BCC subtypes. The slope of the exponential attenuation of the signal in the upper part of the epidermis was very high in benign nevi. The more malignant the lesion the lower the slope. Thickness measurements of epidermis and papillary dermis could be performed by m_HD-OCT, based on a cross-sectional images and their corresponding en face image. More accurate measurements of epidermal and papillary dermal thickness could be performed based on the optical analysis of a skin volume by o_HD-OCT. The diagnostic potential of HD-OCT in comparison with dermoscopy, RCM and C-OCT could be assessed regarding i) melanoma, ii) BCC differentiation from BCC imitators and BCC sub-differentiation and iii) SCC differentiation from AK. A much higher diagnostic potential could be demonstrated for o_HD-OCT in comparison with m_HD-OCT concerning melanoma detection. The diagnostic potential of HD-OCT to discriminate BCC from clinical BCC imitators was moderate. However, HD-OCT seemed to have high potential in sub-differentiation of BCC subtypes: i) it seemed to be the best technique to include and exclude a superficial BCC, ii) the technique appeared to be the best approach to exclude nodular BCC, and iii) HD-OCT looked to be the best technique to include an infiltrative BCC. Finally, HD-OCT has proven to be a powerful method to discriminate AK from SCC.Conclusions. HD-OCT is able to capture real time 3-D imaging with a sufficiently high optical resolution and penetration depth to allow the visualization of cells in and ex vivo in their micro-architectural context. At the same time, HD-OCT permits the recognition of patterns and structures in a sufficiently large volume of skin (1.5 mm³). HD-OCT closes therefore the gap between RCM with a high resolution but low penetration depth and C-OCT with a low resolution but high penetration depth. Moreover, HD-OCT permits, in contrast to RCM and C-OCT, the real time in vivo analysis of optical properties of the skin. HD-OCT seems to be a promising tool for early diagnosis of melanoma, BCC sub-differentiation and differentiation between SCC and AK.Future perspectives. Multicenter validation studies are needed to determine the diagnostic performance of this promising new technology, especially in other clinical settings combining both morphological and optical property analysis. This combined analysis could be a valuable method not only for diagnosis, monitoring and therapeutic guidance of dermatologic diseases but it could also be helpful in the management of non-dermatologic conditions such as diabetic micro-angiopathy, infantile cystinosis or even osteoporosis. / Doctorat en Sciences médicales (Santé Publique) / info:eu-repo/semantics/nonPublished