Melanocytic nevi with special features: clinical-dermoscopic and reflectance confocal microscopic-findings

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Abstract

Histopathology is considered the 'gold' standard for the diagnosis and classification of melanocytic nevi, but the widespread use of in vivo diagnostic technologies such as dermoscopy and reflectance confocal microscopy (RCM), has enriched profoundly the knowledge regarding the morphological variability in nevi. This is because most morphological observations made via these in vivo tools are closely correlated with features seen in histopathology. Dermoscopy has allowed for a more detailed classification of nevi. As such, dermoscopy identifies four main morphologic groups (i.e. globular, reticular, starburst and structureless blue nevi), one group of nevi located at special body sites (i.e. face, acral, nail) and one group of nevi with special features. This latter category consists of nevi of the former categories, which are typified by peculiar clinical-histopathological findings. They can be subdivided into 'melanoma simulators' including combined nevi, recurrent nevi and sclerosing nevus with pseudomelanomatous features, 'targetoid' nevi (i.e. halo, cockade, irritated targetoid haemosiderotic and eczematous nevus) and uncommon histopathological variants such as desmoplastic, white dysplastic or ballon cell nevus. While the dermoscopic and RCM patterns of the former categories have been studied in detail, little is currently known about the clinical morphology of the heterogeneous group of 'special' nevi. In this article, we describe the clinical, dermoscopic and RCM features of 'special' nevi and review the current literature on this group of melanocytic proliferations.

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Dominant role of the niche in melanocyte stem-cell fate determination.

Shin-ichi Nishikawa, Yann Barrandon, Hisahiro Yoshida … (2002)

Stem cells which have the capacity to self-renew and generate differentiated progeny are thought to be maintained in a specific environment known as a niche. The localization of the niche, however, remains largely obscure for most stem-cell systems. Melanocytes (pigment cells) in hair follicles proliferate and differentiate closely coupled to the hair regeneration cycle. Here we report that stem cells of the melanocyte lineage can be identified, using Dct-lacZ transgenic mice, in the lower permanent portion of mouse hair follicles throughout the hair cycle. It is only the population in this region that fulfils the criteria for stem cells, being immature, slow cycling, self-maintaining and fully competent in regenerating progeny on activation at early anagen (the growing phase of hair follicles). Induction of the re-pigmentation process in K14-steel factor transgenic mice demonstrates that a portion of amplifying stem-cell progeny can migrate out from the niche and retain sufficient self-renewing capability to function as stem cells after repopulation into vacant niches. Our data indicate that the niche has a dominant role in the fate determination of melanocyte stem-cell progeny.

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The impact of in vivo reflectance confocal microscopy for the diagnostic accuracy of melanoma and equivocal melanocytic lesions.

Giovanni Pellacani, Pascale Guitera, Caterina Longo … (2007)

In vivo confocal reflectance microscopy recently showed promising results for melanoma (MM) diagnosis on a limited series. The aim of the study was to evaluate the sensitivity and specificity of confocal features for the diagnosis of MM 351 equivocal melanocytic lesions (136 MMs and 215 nevi) were evaluated for 37 confocal features by two blinded expert observers. Chi2 test, multivariate discriminant analysis and binary logistic regression were performed for the identification of the significant features and for testing newly created diagnostic models. Melanomas were mostly characterized by epidermal disarray and pagetoid cells in the epidermis, non-edged papillae, and cellular atypia at the junction, and atypical nests and bright nucleated cells in the upper dermis. On the other hand, regular dermal-epidermal architecture, and absence of pagetoid infiltration and atypical cells were suggestive of benign lesions. Five out of 136 melanomas, with mildly atypical melanocytes and occasional pagetoid cells at histopathology, were not diagnosed by confocal microscopy. Nevertheless, new diagnostic models showed no significant improvement compared with the previously proposed confocal microscopy algorithm. Owing to the visualization of cellular aspects, confocal microscopy seems useful for second level examination of clinically and dermoscopically equivocal lesions.

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In vivo confocal microscopic and histopathologic correlations of dermoscopic features in 202 melanocytic lesions.

Sonia Segura, Sara Bassoli, Susana Puig … (2008)

To identify in vivo microscopic substrates of the dermoscopic patterns of melanocytic lesions and to correlate them with histopathologic features. Before excision, lesion areas that showed characteristic dermoscopic patterns were imaged by dermoscopy and confocal microscopy and directly correlated with histopathologic features. Departments of Dermatology of the University of Modena and Reggio Emilia and Hospital Clínico of Barcelona, between July 2006 and March 2007. Patients Patients with 202 melanocytic lesions, corresponding to 76 melanomas, 114 nevi, and 12 Spitz or Reed nevi. Correlation of dermoscopic patterns in melanocytic lesions with confocal microscopic findings and conventional histopathologic findings. Characteristic architectural and cytologic substrates were identified in vivo with the use of confocal microscopy and correlated with histopathologic features. Pigment network atypia was evidenced through confocal microscopy as a disarrangement of dermoepidermal junction architecture and cellular atypia. Pigmented globules consisted of cell clusters, corresponding to melanocytic nests identified on histopathologic analysis. Black dots correlated with intraepidermal reflective spots or with large pagetoid cells in nevi and melanoma, respectively. Blue structures usually consisted of numerous pleomorphic cells, corresponding to malignant melanocytes and inflammatory cells in melanomas, whereas plump bright cells, corresponding to melanophages on histopathologic analysis, characterized benign lesions. Within regression, a retiform distribution of collagen fibers, which sometimes intermingled with melanophages and rarely with nucleated cells, was observable. The knowledge of the cytologic and architectural aspects of the different dermoscopic patterns, as they appear by in vivo confocal microscopy, may guide the user to the identification of specific substrates in melanocytic lesions and consequently the interpretation of the dermoscopic features.