‘Eruptive’ amelanotic compound nevi in children with facial freckles and pale skin colour: more than an occasion?

BACKGROUND: RCM (reflectance confocal microscopy) is a noninvasive, high-resolution technology that has been proven to improve the diagnostic accuracy over clinical examination in several skin diseases. OBJECTIVE: The aim of this article is to describe the morphologic features of halo nevi (HN) observed with RCM and correlate them with their dermoscopic characteristics. METHOD: Nine patients with the clinical diagnosis of HN were assessed with RCM. A second assessment was performed up to 12 months later. Dermoscopic global patterns were obtained and correlated with the RCM findings. RESULTS: In five (55.6%) cases, pagetoid cells were observed. Nonedged dermal papilla and junctional thickening were found in three (33%) cases. Nucleated cells in the dermal papillae and plump bright cells were observed in seven (77.8%) and six (66.7%) cases, respectively.   CONCLUSION: Our study shows that HN observed by RCM can show atypical features that overlap with those observed on atypical melanocytic lesions and malignant melanoma.

In vivo reflectance confocal microscopy (RCM) provides high-resolution, real-time optical sections of the skin in a non-invasive manner, allowing visualization of the skin in its native state. Highly reflective skin components including melanin, collagen and keratin appear bright (white) in RCM images. RCM examination of solar lentigines is known to show features that correlate well with histologic findings such as supranuclear melanin caps, but there are a limited number of reports on melanocyte dendrites. In this study, we utilized RCM to investigate the melanocyte dendricity and distribution within solar lentigines. Seventeen healthy Japanese females who had fairly large solar lentigines on their faces were recruited to join our clinical study, and we examined them by using RCM on their non-lesional areas, and the inside and the outer rim of the lesional areas. As a result, we discovered that dendritic melanocytes were rarely seen in the center of a solar lentigo (SL), but were seen at a very high frequency in the outer rim of a SL. The results suggest that the melanocytes are more active at the edge of a SL, produce more melanin, and often spread their dendrites widely in a horizontal direction. The findings in this report might shed light on the dynamic pathomechanisms of solar lentigines in vivo.

BACKGROUND: Lichen planus-like keratosis (LPLK) may be difficult to differentiate from melanoma and other skin cancers on sun-damaged skin based on clinical and dermoscopic examination. Reflectance confocal microscopy (RCM) allows evaluation of skin lesions at high resolution. OBJECTIVES: The aim of this study was to identify criteria for specific diagnosis of LPLK using in vivo RCM. METHODS: Lesions included in the study were derived from patients presenting for skin examination at a private dermatology practice specializing in skin cancer. We retrospectively analysed RCM features of 28 biopsy-proven LPLK and compared them to RCM findings in skin cancers on sun-damaged skin, including five in situ squamous cell carcinomas, six actinic keratoses, seven superficial basal cell carcinomas and eight melanomas. RESULTS: The main RCM features of LPLK and their relative frequencies were: (i) typical honeycomb pattern of the spinous layer (78.6%); (ii) elongated cords and/or bulbous projections at the dermal-epidermal junction (75%); and (iii) numerous plump-bright cells and/or bright stellate spots in the superficial dermis (92.9%). These RCM features correlated with the following histopathological findings respectively: (i) spinous-granular layers without significant atypia of keratinocytes; (ii) elongated, bulbous rete ridges; and (iii) dense infiltration of melanophages and lymphocytes in superficial dermis. We propose diagnostic criteria that classify correctly 71.4% of LPLK, while avoiding misclassification of any of the skin cancers in the present series as LPLK. CONCLUSIONS: We identified RCM criteria for diagnosis of LPLK that correlate well with histopathological findings and that allow differentiation of LPLK from skin cancer.