Optical coherence tomography (OCT) represents a non-invasive imaging technology, which may be applied to the diagnosis of non-melanoma skin cancer and which has recently been shown to improve the diagnostic accuracy of basal cell carcinoma. Technical developments of OCT continue to expand the applicability of OCT for different neoplastic and inflammatory skin diseases. Of these, dynamic OCT (D-OCT) based on speckle variance OCT is of special interest as it allows the in vivo evaluation of blood vessels and their distribution within specific lesions, providing additional functional information and consequently greater density of data. In an effort to assess the potential of D-OCT for future scientific and clinical studies, we have therefore reviewed the literature and preliminary unpublished data on the visualization of the microvasculature using D-OCT. Information on D-OCT in skin cancers including melanoma, as well as in a variety of other skin diseases, is presented in an atlas. Possible diagnostic features are suggested, although these require additional validation.

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SummaryBackground Nodular lesions pose diagnostic challenges because nodular melanoma may simulate all kinds of melanocytic and nonmelanocytic lesions. Reflectance confocal microscopy (RCM) is a novel technique that allows visualization of the skin at nearly histological resolution although limited laser depth penetration hampers visualization of the deep dermis. Objectives We sought to assess whether the diagnostic accuracy of RCM was comparable to histopathology for the diagnosis of nodular lesions, and to identify possible limitations of this technique. Methods We retrospectively evaluated 140 nodules by means of RCM while blinded from the histopathological diagnosis. At the end of the study the patient codes were broken and the evaluations were matched with histopathological diagnosis before performing statistical analysis. Results The study consisted of 140 nodular lesions (23 'pure' nodular melanomas, nine melanoma metastases, 28 BCCs, six invasive SCCs, 32 naevi, 14 seborrhoeic keratoses, 17 dermatofibromas, five vascular lesions and six other lesions). RCM correctly diagnosed 121 of 140 lesions (86Á4%); eight of 140 (5Á7%) lesions revealed discordance between histopathology and confocal microscopy. Eight of the 140 (5Á7%) cases were not evaluable by means of RCM due to the presence of ulceration or hyperkeratosis and three cases showed a nonspecific pattern. Interestingly, confocal microscopy reached a 96Á5% sensitivity and 94Á1% specificity (area under curve 0Á970) (95% CI 0Á924-1Á015) (P < 0Á001) for the diagnosis of melanoma. Conclusions The study is retrospective and lesions were not included on the basis of their diagnostic difficulty. Despite the limited laser depth penetration of RCM, this imaging tool represents an effective instrument in diagnosing nodular lesions; however, for fully ulcerated lesions or when a marked hyperkeratosis is present, biopsy should always be performed. Prospective studies on difficult-todiagnose nodules should be performed to analyse further the pros and cons of RCM in skin cancer diagnosis.

The fast and reliable characterization of acne lesions and identification of subclinical alterations in acne-prone skin through confocal examination, corresponding to infundibular hyper-keratinization, may have important clinical consequences in the assessment of acne severity, therapeutic decisions and treatment efficacy monitoring.

The progressive reduction in the clinical scores was correlated with the improvement of the RCM parameters. RCM study of acne skin showed a different timing for inflammatory and hyperkeratotic components to achieve a significant reduction during topical therapy with the association of retinoid and antibacterial molecules. The microscopic changes observed showed the regularization of the skin and the improvement of acne related features. RCM may represent a useful tool for the objective assessment of treatment efficacy and individual response evaluation.

The characterization of acne lesions and the identification of vascular pattern in acne lesions through D-OCT, corresponding to blood vessel dilation and inflammatory associated hyper-vascularization, may have important clinical consequences in the assessment of acne severity, therapeutic decisions and treatment efficacy monitoring.

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The subtype of basal cell carcinoma (BCC) influences the choice of treatment. Optical coherence tomography (OCT) is a non-invasive imaging tool, and a recent development of an angiographic version of OCT has extended the application of OCT to image the cutaneous microvasculature (so-called dynamic OCT, D-OCT). This study explores D-OCT's ability to differentiate the common BCC subtypes by microvascular and structural imaging. Eighty-one patients with 98 BCC lesions, consisting of three subtypes: 27 superficial BCC (sBCC), 55 nodular BCC (nBCC) and 16 infiltrative BCC (iBCC) were D-OCT scanned at three European dermatology centres. Blinded evaluations of microvascular and structural features were performed, followed by extensive statistical analysis of risk ratio (RR) and multiple correspondence analysis. nBCC lesions displayed most characteristic structural and vascular features. Serpiginous vessels, branching vessels, vessels creating a circumscribed figure and sharply demarcated hyporeflective ovoid structures in the dermis were all associated with a higher risk of the subtype being nBCC. The presence of highly present lines and dark peripheral borders at the margin of ovoid structures was negatively associated with iBCC. Lastly, the finding of hyporeflective ovoid structures protruding from epidermis correlated with sBCC. We identified various microvascular and structural D-OCT features that may aid non-invasive identification of BCC subtypes. This would allow clinicians to individualize and optimize BCC treatment as well as aid follow-up of non-surgical treatment.