Dermoscopy for Dermatopathologists

Prior to the 1970s dermatologists had the advantage of analyzing the clinical morphology of lesions with their histopathology-trained eye and the microscopic morphology with their clinically trained eye. With the creation of dermatopathology as a subspecialty in the 1970s, clinical dermatology and histopathology uncoupled. This separation has made clinical-pathologic correlation more difficult. The importance of integrating both the clinical and pathology findings for accurate diagnosis is widely acknowledged and the reason for the necessity of clinical-pathologic conferences, which attempt to reconcile discordant or unusual findings. One potential reason for diagnostic errors stems from the inherent limitation of tissue processing and step sectioning of specimens, in which the focus of the diagnostic pathology may simply not get captured. One has to bear in mind that routine sectioning of 4-mm biopsy makes only approximately 0.1% of the entire lesion available for review. Multiple studies have shown that providing the pathologist with clinical and/or dermoscopic photographs can help guide the way the tissue is sectioned to best answer the diagnostic question. Clinicians can assist in this regard by providing images indicating where to step section or by marking the area within the specimen to ensure that sectioning occurs through the area of interest/concern. This can be accomplished via use of marking sutures, ink, or punch scoring the area of interest. This process is more accurate when performed using dermoscopy guidance.

Dermoscopy is a handheld instrument consisting of a magnification lens (approximately 10×) attached to a polarized or nonpolarized light source. It permits in vivo and en face visualization of microscopic structures in the skin located in the epidermis and papillary dermis. Dermoscopy has been shown to increase the clinician's diagnostic accuracy, improving both sensitivity and specificity of melanoma diagnosis. Because dermoscopy assists in differentiating melanocytic nevi from melanoma, it may prove useful during the grossing of skin specimen to identify the diagnostically most informative area ( Fig. 28.1 ) and order upfront more levels for a more detailed analysis. Thorough sampling is important to avoid misdiagnosis related to sampling errors in the pathology laboratory (i.e., missing focal melanoma arising in a nevus) (see Fig. 28.1D ). Dermoscopy may help identify structures that point toward melanoma, and this information can then help streamline the tissue processing and sectioning process, thereby minimizing the risk of not examining microscopically a critical diagnostic part of the lesion.

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Examples of dermoscopic images taken from melanocytic lesions concerning for melanoma. These lesions show asymmetrically-distributed dermoscopic structures such as peripheral atypical network (A), off-centered blotch (B), or multiple off-centered blotches and peripheral atypical network (C). Panel D shows a previously biopsied melanocytic lesion that revealed a melanoma with a Breslow depth of 1 mm. Despite the obvious pigmentation in the lesion on dermoscopic exam after the biopsy, the reexcised specimen was read as a scar after histologic analysis. Due to the dermoscopic and pathologic disconcordance, additional sections were obtained showing residual melanoma, revealing incorrect initial grossing. All these cases could have benefited from ex vivo dermoscopy to guide step sectioning.

Although using dermoscopic information to guide the processing skin specimens can help pathologists in selected cases render the correct diagnosis, the success of dermoscopically guided tissue processing depends on the expertise of clinicians and their knowledge in dermoscopy to accurately mark the area of greatest concern. They not only need to know the dermoscopic structures and their histopathologic correlations but also have time to annotate the image or specimen. Many physicians do not have cameras or the time or expertise to perform this task in a meaningful manner. One way to circumvent the need for a clinician's input is for the pathologist or the histotechnician to perform the task. Because most dermoscopic structures have direct histopathologic correlates and can be visualized ex vivo, it is possible for the pathologist to inspect the lesion at the grossing table with dermoscopy and, based on the findings, decide the location or locations most appropriate to section ( Fig. 28.2 ). Besides helping arrive at the most accurate diagnosis, there may also be an added benefit in limiting the number of step sections required to render this diagnosis. It may prove to be cost effective in selected cases to perform ex vivo dermoscopy (EVD) and obtain one or two sections as opposed to multiple step sections. Apart from such practical considerations for the laboratory, learning dermoscopy is beneficial for pathologists. At a minimum, knowledge in dermoscopy should improve their ability to communicate with clinicians and helps them better correlate microscopic and clinical findings.

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Pathologist with dermoscope attached to a smartphone performing ex vivo dermoscopy on a previously formalin-fixed specimen to guide step sectioning.