Dermoscopic structures and their histopathological correlation
This chapter defines dermoscopic criteria such as colors and structures and their significance, as well as the histopathologic correlates to dermoscpic criteria and the differences between them.
It has the following subchapters:
Dermoscopy evaluates the lesion in all its extensions on a horizontal plane. This can allow the selection of the best area to biopsy in large lesions, as well as giving information to the pathologist of the most representative area to section (Bauer et al., 2001; Soyer et al., 2005). Improvement in sampling can occur either using dermoscopy in the clinical setting (Bauer et al., 2001) or by using dermoscopy directly in the excised specimen in the laboratory (ex vivo dermoscopy) (Marc Haspeslagh et al., 2016; Scope et al., 2007). Ex vivo dermoscopy (EVD) is a valuable tool since most dermoscopic features are visible even after formalin fixation (Marc Haspeslagh et al., 2016). It can be extremely helpful when scarce or no clinical information is available, in this setting EVD can improve the diagnosis of challenging melanocytic lesions (Amin and Fraga, 2012; Cabete et al., 2016). EVD is very useful when evaluating large and complex pigmented lesions since clinicians or pathologists can mark the areas of interest using “derm dotting” in order to analyze them properly under the microscope (Haspeslagh et al., 2013). EVD can identify melanomas missed with conventional step sectioning, improves the staging of melanomas (Cabete et al., 2016), increase the detection of positive margins in keratinocyte carcinomas (Marc Haspeslagh et al., 2016), decreases the diagnostic turnaround time (Marc Haspeslagh et al., 2016) and potentially reduces the costs of histologic processing. Dermoscopy of the hair and scalp can be a valuable tool in the diagnosis and follow-up of these disorders (Richarz et al., 2018; Tosti, 2007), It can also guide the biopsy procedure, allowing identification of even individually affected follicles in early or focal cicatricial alopecia. The trichoscopy guided biopsies can reach a definitive pathological diagnosis in 95% of the cases (Miteva and Tosti, 2013).
Dermoscopic structures observed in melanocytic neoplasms are not only important for diagnosis but can also provide valuable prognostic information such as mitotic activity (Deinlein et al., 2017; Ribero et al., 2017), Breslow >0.75mm (Argenziano et al., 1997a; Silva et al., 2013), dermal invasion (Balagula et al., 2012) or presence of lymph node metastases (table 1) (González-Álvarez et al., 2015).
Dermoscopy can help identify different subtypes of skin cancers, which can have important therapeutic implications. For example, dermoscopic structures more frequently associated with non-superficial, mostly nodular BCC, are blue-ovoid nests, arborizing vessels, and ulceration, and warrant surgical excision. On the other hand, the presence of serpentine vessels, leaflike areas or multiple small erosions in a flat lesion are associated with superficial BCC (table 2) and can be treated non-surgically (Aimilios Lallas et al., 2014) (Ahnlide et al., 2016). Dermoscopy may also help predict the response to treatment: the presence of ulceration in a non-treated BCC has been associated with a good response to imiquimod (Urech et al., 2017). In squamous cell carcinoma (SCC), dermoscopy can help differentiate between actinic keratosis and Bowen's disease (Cameron et al., 2010; Zalaudek et al., 2012), and to predict the degree of differentiation of infiltrating SCCs (A. Lallas et al., 2015; Zalaudek et al., 2012). In melanoma, dermoscopy can predict genetic mutations associated with this tumor which may have relevant therapeutic implications with the advent of the new targeted drugs (table 1) (Bombonato et al., 2017; Pozzobon et al., 2014; Sanchez et al., 2014). Dermoscopy of skin infections and infestations can help to guide the treatment and to monitor the clinical response in different pathologies such as scabies, vulgar warts, molluscum contagiosum, pediculosis, tinea nigra, among others (Zalaudek et al., 2008).
