Combining Reflectance Confocal Microscopy with Optical Coherence Tomography for Noninvasive Diagnosis of Skin Cancers via Image Acquisition

Skin cancer is one of the most common cancers worldwide. Diagnosis relies on visual inspection and dermoscopy followed by biopsy for histopathological confirmation. While the sensitivity of dermoscopy is high, the lower specificity results in 70%-80% of the biopsies being diagnosed as benign lesions on histopathology (false positives on dermoscopy). Reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) imaging can noninvasively guide the diagnosis of skin cancers. RCM visualizes cellular morphology in en-face layers. It has doubled the diagnostic specificity for melanoma and pigmented keratinocytic skin cancers over dermoscopy, halving the number of biopsies of benign lesions. RCM acquired billing codes in the USA and is now being integrated into clinics. However, limitations such as the shallow depth (~200 µm) of imaging, poor contrast for nonpigmented skin lesions, and imaging in en-face layers result in relatively lower specificity for the detection of nonpigmented basal cell carcinoma (BCCs) — superficial BCCs contiguous with the basal cell layer and deeper infiltrative BCCs. In contrast, OCT lacks cellular resolution but images tissue in vertical planes down to a depth of ~1 mm, which allows the detection of both superficial and deeper subtypes of BCCs. Thus, both techniques are essentially complementary. A "multi-modal," combined RCM-OCT device simultaneously images skin lesions in both en-face and vertical modes. It is useful for the diagnosis and management of BCCs (nonsurgical treatment for superficial BCCs vs. surgical treatment for deeper lesions). A marked improvement in specificity is obtained for detecting small, nonpigmented BCCs over RCM alone. RCM and RCM-OCT devices are bringing a major paradigm shift in the diagnosis and management of skin cancers; however, their use is currently limited to academic tertiary care centers and some private clinics. This paper familiarizes clinicians with these devices and their applications, addressing translational barriers into routine clinical workflow.