Dermoscopy and reflectance confocal microscopy, a synergistic approach: The (very) difficult differential diagnosis of flat solitary unpigmented lesions demonstration

Abstract

Diagnosis of solitary flat unpigmented skin lesions is a challenge since, aside many benign counterparts, these lesions, most often tumours, may correspond to several skin cancers including melanoma.¹ Moreover, dermoscopy (DS) of totally unpigmented tumours, at the noticeable exception of vascular tumours and unlike pigmented ones, relies on indirect criteria.² These may be reflecting either the volumetric impact of the tumour on normal vessels of the dermal papilla (hairpin-like vessels, coma like vessels, dotted vessels, glomerular vessels) or of the superficial sub epidermal horizontal plexuses (arborizing and coronal vessels) or the presence of a neo-vascularization produced by the stroma of the tumour (so called ‘atypical vascular patterns’ encompassing milky red areas, serpentine vessels and polymorphic vessels). Needless to say that these two categories of indirect vascular symptoms are neither specific of any pathological entity (at the remarkable exception of clear cell acanthoma maybe, that does not represent a major public health problem anyway) nor of a nosographic category of lesion (erythema, benign or malignant tumour). In vivo reflectance confocal microscopy (RCM) adds to diagnostic accuracy yet its additional benefit compared with dermoscopy alone was not clearly demonstrated by a systematic review.³

The originality of the study by Spadafora et al.⁴ published in this issue was to combine DS + RCM in order to compensate one-another the possible insufficiencies, inherent to these two techniques themselves, in the difficult differential diagnosis of amelanotic or hypomelanotic flat skin tumours. The reader will find in their text that this approach was successful and that further work is planned to validate their model. There is no need to develop this point here.

More interestingly in our view for an editorial comment, the reasons for such a synergy could be worth the trial for some speculations in order to propose a potential list of similarly promising combined approaches in other difficult diagnostic challenges in tumoral as well as inflammatory dermatology. Spadafora et al. underlined that, in the studied situation, DS was particularly efficient in disclosing papillary and reticular dermis ‘architectural’ changes mainly affecting the red dermoscopy chromophore (i.e. haemoglobin containing cells in vessels) that was more difficult to appreciate within the RCM narrow fields. On the opposite, RCM was adding a ‘cellular level’ by evidencing lightly pigmented or unpigmented cells lacking by definition the black chromophore (i.e. melanin) that could have revealed them to the eye of the dermoscopy examiner. Synergistic approaches of these two non-invasive skin-imaging techniques can certainly be extrapolated from their findings in many other conditions including the difficult differential diagnosis of mycosis fungoides or of the GVHD. Moreover, other non-invasive skin-imaging instruments, including very high-resolution ultrasound, optical coherence tomography, RAMAN spectrometry, etc. …, may very well also have such a synergistic impact when combined to dermoscopy that, however, will probably keep for long years its great advantage of a fast whole-surface tool to analyse abnormal skin architectural changes caused by tumours, infections, infestations and inflammatory phenomena. Additional multi-approach algorithms can also be imagined, probably not to replace histopathology, but to offer an alternative to multiple or sequential tissue sampling during the pre-therapeutic evaluation or the follow-up of many skin tumours and diseases including morphoea-like basal cell carcinoma or palisading granulomas for example.

Dermoscopy and digital dermoscopy equipment given to our institution by 3-GEN, CASIO, C-CUBE, FOTOFINDER, HEINE. Pr Thomas is the author and co-author of several dermoscopy textbooks. Dr. Pham and Pr Thomas are editors of a dermatology textbook.